235 E. Main Street
Midland, Michigan 48640
(989) 839-5350
(Address, Including Zip Code, and Telephone Number, Including Area Code, of Registrant's Principal Executive Offices)

          Approximate date of commencement of proposed sale of the securities to the public: As soon as practicable after this Registration Statement becomes effective.

          If the securities being registered on this form are being offered in connection with the formation of a holding company and there is compliance with General Instruction G, check the following box:   o

          If this form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.   o

          If this form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.   o

          Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of "large accelerated filer," "accelerated filer," and "smaller reporting company" in Rule 12b-2 of the Exchange Act.

          If applicable, place an X in the box to designate the appropriate rule provision relied upon in conducting this transaction:
          Exchange Act Rule 13e-4(i) (Cross-Border Issuer Tender Offer)           o
          Exchange Act Rule 14d-1(d) (Cross-Border Third-Party Tender Offer)           o

          The board of directors of O.A.K. Financial Corporation is furnishing this prospectus and proxy statement and the accompanying form of proxy on or about [ April 15 ] , 2010, to the shareholders of O.A.K. to solicit proxies to vote at a special meeting of O.A.K.'s shareholders to be held on [ May 20 ] , 2010, at [ The Pinnacle Center, 3330 Highland Drive, Hudsonville, Michigan 49426 ] at [ • ] a.m. local time and at any adjournments of the special meeting. At the special meeting, the shareholders of O.A.K. will consider and vote upon a proposal to approve a merger agreement with Chemical Financial Corporation, under which O.A.K. would be merged with and into Chemical. The board of directors of O.A.K. has adopted the merger agreement. Chemical's board of directors has adopted the merger agreement and Chemical is not required to submit the merger agreement to its shareholders for approval.

          This prospectus and proxy statement, when delivered to shareholders of O.A.K., is a prospectus of Chemical relating to an offering of Chemical common stock. This offering is made only to holders of O.A.K. common stock.

          If the merger agreement is approved and the merger is completed, each outstanding share of O.A.K. common stock that you hold will be converted into the right to receive 1.306 shares of Chemical common stock (plus cash in lieu of any fractional share). Chemical's common stock is listed on the NASDAQ Global Select Market under the trading symbol "CHFC."

          O.A.K.'s board of directors has unanimously adopted the merger agreement and approved and declared advisable the merger and other transactions contemplated by the merger agreement, and unanimously recommends that O.A.K. common shareholders vote "FOR" approval of the merger agreement.

          Please read this prospectus and proxy statement carefully because it contains important information about the merger. Read carefully the risk factors relating to the merger beginning on page 9. You can also obtain additional information about Chemical and O.A.K. from documents that each of us has filed with the Securities and Exchange Commission at www.sec.gov.

          In the opinion of Donnelly Penman & Partners, the terms of the merger are fair, from a financial point of view, to the shareholders of O.A.K. See "The Merger-Fairness Opinion of Donnelly Penman & Partners."

          Your vote is important. Approval of the proposed merger agreement requires the affirmative vote of a majority of the outstanding shares of O.A.K. common stock. Please sign and date the enclosed proxy and mail it promptly in the enclosed envelope, regardless of whether or not you expect to attend the meeting in person.

          The shares of Chemical common stock to be issued in the merger are not deposits or savings accounts or other obligations of any bank or savings association, and are not insured by the Federal Deposit Insurance Corporation or any other governmental agency. Chemical common stock is subject to investment risks, including possible loss of value.

          NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR DETERMINED IF THIS PROSPECTUS AND PROXY STATEMENT IS TRUTHFUL OR COMPLETE. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

This prospectus and proxy statement is dated [ April 15 ] , 2010.

TABLE OF CONTENTS

Chemical has filed a registration statement with the Securities and Exchange Commission (the " Commission " or the " SEC ") relating to the Chemical common stock offered in connection with the proposed merger described in this prospectus and proxy statement. This prospectus and proxy statement does not contain all of the information set forth in the registration statement, certain portions of which are omitted in accordance with the rules and regulations of the Commission. Reference is hereby made to the registration statement and exhibits thereto for further information about Chemical, O.A.K., and their respective securities. The registration statement is available at http://www.sec.gov. O.A.K. shareholders can also obtain copies of all or part of the registration statement without charge upon written or oral request directed to Lori A. Gwizdala, Chief Financial Officer, Chemical Financial Corporation, 333 East Main Street, P.O. Box 569, Midland, Michigan 48640, (800) 867-9757. A shareholder making such a request must request the information at least five business days before the date they must make their investment decision to ensure timely delivery. Accordingly, the deadline for an O.A.K. shareholder to make a request is [May 13], 2010.

2445 84 ^th Street, S.W.
Byron Center, Michigan 49315

NOTICE OF SPECIAL MEETING OF SHAREHOLDERS

To the shareholders of O.A.K. Financial Corporation:

          A special meeting of shareholders of O.A.K. Financial Corporation will be held on [ May 20 ] , 2010, at [ The Pinnacle Center, 3330 Highland Drive, Hudsonville, Michigan 49426 ] at [ • ] a.m. local time, for the following purposes:

          1.          To consider and vote upon a proposal to approve a merger agreement between O.A.K. Financial Corporation and Chemical Financial Corporation.

          2.          To transact such other business as may properly come before the meeting.

          The board of directors has established the close of business on [ April 7 ] , 2010, as the record date for the determination of shareholders entitled to notice of and to vote at the meeting and any adjournment of the meeting.

          O.A.K.'s board of directors has unanimously adopted the merger agreement and approved and declared advisable the merger and other transactions contemplated by the merger agreement, and unanimously recommends that O.A.K. common shareholders vote "FOR" approval of the merger agreement.

YOUR VOTE IS IMPORTANT. EVEN IF YOU PLAN TO
ATTEND THE MEETING, PLEASE SIGN, DATE AND
RETURN THE ENCLOSED PROXY PROMPTLY .

QUESTIONS AND ANSWERS ABOUT THE MERGER

Use of Terms

          Unless the context otherwise requires, in this prospectus and proxy statement " Chemical ," "we," "our," or "us" refers to Chemical Financial Corporation, " O.A.K. " refers to O.A.K. Financial Corporation, and "you" and "your" refer to each shareholder of O.A.K. Financial Corporation.

          This summary highlights selected information from this prospectus and proxy statement. It may not contain all of the information that is important to you. For a more complete understanding of the merger between Chemical and O.A.K. we urge you to carefully read and consider this entire document, the merger agreement (attached as Appendix A to this prospectus and proxy statement) and the other documents we refer you to or incorporate by reference into this prospectus and proxy statement.

The Companies

Chemical

Chemical Financial Corporation
235 E. Main Street
Midland, Michigan 48640
(989) 839-5350

          Chemical is a financial holding company with its business concentrated in a single industry segment - commercial banking. Chemical is headquartered in Midland, Michigan, and is the parent company of Chemical Bank. Chemical Bank operates 129 banking offices spread over 31 counties in Michigan's lower peninsula.

O.A.K.

O.A.K. Financial Corporation
2445 84 ^th Street, S.W.
Byron Center, Michigan 49315
(616) 588-7418

          O.A.K. is a bank holding company headquartered in Byron Center, Michigan. O.A.K. is the parent company of Byron Bank. Byron Bank has 14 banking offices serving 14 communities in Kent, Ottawa and Allegan Counties in west Michigan.

Summary of Certain Aspects of the Merger

Structure of the Merger (see page 33)

          If the merger is completed, O.A.K. will be merged with and into Chemical. The surviving corporation will be Chemical. The surviving corporation will own Chemical Bank and Byron Bank and all of the other assets of O.A.K. and Chemical.

What O.A.K. Shareholders will Receive in the Merger (see page 33)

          If the merger is completed as planned, subject to adjustment in certain limited circumstances, you will receive 1.306 shares of Chemical common stock for each share of O.A.K. common stock.

          Chemical will not issue fractional shares of Chemical common stock in the merger. An O.A.K. shareholder who would otherwise be entitled to receive a fraction of a share of Chemical common stock in the merger will instead receive an amount of cash determined by multiplying that fraction by the average closing price of Chemical common stock for the 20 trading days ending on the sixth business day before the closing date of the merger on which shares of Chemical common stock were actually traded in transactions reported on the NASDAQ Stock Market.

Adjustment of Merger Consideration (see page 33)

          The merger consideration is subject to adjustment in certain limited circumstances, including, among others, if the aggregate of certain loan loss and shareholders' equity levels exceed $10,000,000 by an amount up to a maximum of $5,000,000.

What Holders of O.A.K. Stock Options will Receive in the Merger (see page 34)

          If the merger is completed as planned, each unexercised stock option to acquire O.A.K. common stock will become an option to purchase the number of shares of Chemical common stock equal to the number of shares of O.A.K. common stock subject to the unexercised option multiplied by 1.306 rounded to the nearest whole share.

Recommendation to O.A.K. Shareholders to Approve the Merger (see page 13)

          O.A.K.'s board of directors has unanimously adopted the merger agreement and approved and declared advisable the merger and other transactions contemplated by the merger agreement and unanimously recommends that you vote "FOR" approval of the merger agreement.

Fairness Opinion (see page 18)

          In deciding to adopt the merger agreement, O.A.K.'s board of directors considered the opinion of its financial advisor, Donnelly Penman & Partners, that the terms of the merger are fair to O.A.K. shareholders from a financial point of view. The written opinion of Donnelly Penman & Partners is attached as Appendix B to this prospectus and proxy statement.

Bank and Subsidiary Consolidation (see page 36)

          At or after the effective time of the merger, Chemical intends to consolidate Byron Bank and Chemical Bank and the corresponding subsidiaries of Byron Bank and Chemical Bank.

Conditions that Must be Satisfied or Waived for the Merger to Occur (see page 37)

          Currently, we expect to complete the merger in the second quarter of 2010. As more fully described in this prospectus and proxy statement and in the merger agreement, the completion of the merger depends on a number of conditions being satisfied or, where permissible, waived. These conditions include, among others, approval by O.A.K. common shareholders and the receipt of all regulatory consents and approvals in connection with the merger. We cannot be certain when, or if, the conditions to the merger will be satisfied or waived, or that the merger will be completed.

Termination of the Merger Agreement (see page 38)

          The merger agreement can be terminated at any time prior to completion of the merger by mutual consent of the boards of directors of Chemical and O.A.K. Also, either party can terminate the merger agreement in various circumstances.

Regulatory Approvals (see page 37)

          Completion of the merger is subject to the approval of the Federal Reserve Board. The applications to obtain such approval have been filed with the Federal Reserve Board as of the date of this prospectus and proxy statement. Although we do not know of any reason why we will not obtain these regulatory approvals in a timely manner, we cannot be certain when or if we will obtain them.

Dissenters' Rights (see page 29)

          Michigan law provides that if the consideration in a merger is shares listed on a national securities exchange, the holders of the stock to be exchanged are not entitled to dissenters' rights. Because Chemical's common stock is listed on a national securities exchange (NASDAQ Stock Market), there are no dissenters' rights.

Material Federal Income Tax Consequences (see page 31)

          The merger is intended to be treated as a reorganization within the meaning of Section 368(a) of the Internal Revenue Code of 1986, as amended, and it is a condition to the respective obligations of Chemical and O.A.K. to complete the merger that each of Chemical and O.A.K. receives a legal opinion to that effect. Accordingly, the merger generally will be tax-free to you for United States federal income tax purposes as to the shares of Chemical common stock you receive in the merger, except for any gain or loss that may result from the receipt of cash in lieu of fractional shares of Chemical common stock you would otherwise be entitled to receive.

          The United States federal income tax consequences described above may not apply to all holders of O.A.K. common stock. Your tax consequences will depend on your individual situation. Accordingly, we strongly urge you to consult your tax advisor for a full understanding of the particular tax consequences of the merger to you.

Market Value of Securities

          Chemical common stock trades on the NASDAQ Global Select Market under the symbol "CHFC" and O.A.K. common stock trades on the Over-the-Counter Bulletin Board Market under the symbol "OKFC.OB."

          The following table sets forth the market value per share of Chemical common stock, the market value per share of O.A.K. common stock and the pro forma equivalent market value per share of O.A.K. common stock on January 7, 2010 (the last business day preceding public announcement of the merger). The equivalent market value for O.A.K common stock is the estimated market value of Chemical common stock to be received in the merger by O.A.K. shareholders for each share of O.A.K. common stock. This value is estimated using a market value of $21.75 per share for Chemical common stock (the closing price of Chemical common stock on January 7, 2010) and using a conversion ratio of 1.306 shares of Chemical common stock for each share of O.A.K. common stock.

          The above table shows only historical comparisons as of January 7, 2010. These comparisons may not provide meaningful information to O.A.K. shareholders in determining whether to approve the merger agreement. We urge you to obtain current market quotations for Chemical and O.A.K. common stock and to review carefully the other information contained in or incorporated by reference into this prospectus and proxy statement in considering whether to approve the merger agreement. See "Where You Can Find More Information" beginning on page 105 and "Incorporation of Certain Information by Reference" beginning on page 105.

Selected Consolidated Historical Financial Data of Chemical (Unaudited)

          The following table shows summarized historical consolidated financial data for Chemical. The table is unaudited. The information in the table is derived from Chemical's consolidated audited financial statements for 2005 through 2008. The financial information for 2009 is derived from Chemical's consolidated unaudited financial statements, which include, in the opinion of Chemical's management, all adjustments, consisting of normal and recurring adjustments, necessary for a fair statement of those results. This information is only a summary. You should read it in conjunction with the consolidated financial statements, related notes, Management's Discussion and Analysis of Financial Condition and Results of Operations, and other information included in Chemical's Annual Report on Form 10-K for the year ended December 31, 2008, which information is here incorporated by reference, and the financial and other information included in this prospectus and proxy statement.

Selected Consolidated Historical Financial Data of O.A.K. (Unaudited)

          The following table shows summarized historical consolidated financial data for O.A.K. The table is unaudited. The information in the table is derived from O.A.K.'s consolidated audited financial statements for 2005 through 2009. This information is only a summary. You should read it in conjunction with the consolidated financial statements, related notes, Management's Discussion and Analysis of Financial Condition and Results of Operations, and other information included in this prospectus and proxy statement.

Summary Selected Pro Forma Combined Data (Unaudited)

          The following table shows selected financial information on a pro forma combined basis giving effect to the merger as if the merger had become effective at the end of the period presented, in the case of balance sheet information, and at the beginning of the period presented, in the case of income statement information. Estimated merger and integration costs expected to be incurred in conjunction with this transaction are not included in the pro forma income statement. The pro forma information reflects the purchase method of accounting.

          Chemical anticipates that the merger will provide the combined organization with financial benefits that include reduced operating expenses and the opportunity to earn more revenue. The pro forma information, while helpful in illustrating the financial characteristics of the combined organization under one set of assumptions, does not reflect these benefits and, accordingly, does not attempt to predict or suggest future results. It also does not necessarily reflect what the historical results of the combined organization would have been had the companies been combined as of the date and during the periods presented.

          You should read this summary pro forma information in conjunction with the information under "Unaudited Pro Forma Combined Condensed Consolidated Financial Statements" beginning on page 41.

Regulatory Capital Ratios

          Under the risk-based capital guidelines presently in effect for banks and bank holding companies, minimum capital levels are based on the perceived risk in the various asset categories. Certain off-balance-sheet instruments, such as loan commitments and letters of credit, require capital allocations. Bank holding companies, such as Chemical and O.A.K., are required to maintain minimum risk-based capital ratios. Chemical's and O.A.K.'s ratios are above the regulatory minimum guidelines. The following table shows capital ratios and requirements as of December 31, 2009.

Comparative Per Share Data

          The following table shows information about earnings per share, dividends per share, and tangible book value per share, combined in a manner that is referred to as "pro forma" information.

          Chemical anticipates that the combined organization will derive financial benefits from the merger that include reduced operating expenses and the opportunity to earn more revenue. The pro forma information, while helpful in illustrating the financial characteristics of the combined organization under one set of assumptions, does not reflect these benefits and, accordingly, does not attempt to predict or suggest future results. The pro forma information also does not necessarily reflect what the historical results of the combined organization would have been had the companies been combined during these periods.

          The information in the following table is based on, and should be read together with, the historical financial information that is presented in Chemical's Annual Report on Form 10-K for the year ended December 31, 2008, which information is here incorporated by reference, the historical financial information that is presented in this prospectus and proxy statement, and the combined condensed consolidated pro forma financial statements presented in this prospectus and proxy statement. See "Where You Can Find More Information" on page 105 and "Incorporation of Certain Information by Reference" on page 105 for instructions on how to obtain the information that has been incorporated by reference.

RISK FACTORS

          In addition to the other information contained in or incorporated by reference into this prospectus and proxy statement, including the matters addressed under the heading "Forward-Looking Statements," you should carefully consider the following risk factors in deciding how to vote on the merger agreement.

The value of the merger consideration will fluctuate with the price of Chemical common stock

          Upon completion of the merger, each share of O.A.K. common stock will be converted into the right to receive merger consideration consisting of 1.306 shares of Chemical common stock pursuant to the terms of the merger agreement. Generally, there will be no adjustment made to the merger consideration you are entitled to receive as a result of fluctuations in the market price of O.A.K. common stock or Chemical common stock. As a result, it is possible that the value of any Chemical common stock you receive in the merger will be different than the value of such shares on the date the O.A.K. board of directors adopted the merger agreement, on the date of the information concerning stock value presented in this prospectus and proxy statement, and on the date that you vote to approve the merger agreement. Stock price changes may result from a variety of factors, including general market and economic conditions, changes in Chemical's business, operations and prospects, and regulatory considerations. Many of these factors are beyond Chemical's control. Accordingly, at the time of the special meeting, you will not necessarily know or be able to calculate the exact value of the shares of Chemical common stock you will receive upon completion of the merger. You should obtain current market quotations for shares of Chemical common stock and for shares of O.A.K. common stock.

Regulatory approvals may not be received, may take longer than expected, or may impose conditions that are not presently anticipated

          The merger must be approved by the Federal Reserve Board, which will consider, among other factors, the competitive impact of the merger, Chemical's financial and managerial resources, and the convenience and needs of the communities to be served. As part of that consideration, we expect that the Federal Reserve Board will review, among other things, capital position, safety and soundness, legal and regulatory compliance matters, and Community Reinvestment Act matters. There can be no assurance as to whether these and other regulatory approvals will be received, the timing of those approvals, or whether any conditions will be imposed.

O.A.K. will be subject to business uncertainties and contractual restrictions while the merger is pending

          Uncertainty about the effect of the merger on employees and customers may have an adverse effect on O.A.K. and consequently on Chemical. These uncertainties may impair O.A.K.'s ability to attract, retain and motivate key personnel until the merger is consummated, and could cause customers and others that deal with O.A.K. to seek to change existing business relationships with O.A.K. Retention of certain employees may be challenging during the pendency of the merger, as certain employees may experience uncertainty about their future roles with Chemical. If key employees depart because of issues relating to the uncertainty and difficulty of integration or a desire not to remain with Chemical, Chemical's business following the merger could be harmed. In addition, the merger agreement restricts O.A.K. from taking specified actions until the merger occurs without the consent of Chemical. These restrictions may prevent O.A.K. from pursuing attractive business opportunities that may arise prior to the completion of the merger. See "The Merger Agreement - Covenants and Agreements" for a summary of certain of the contractual restrictions to which O.A.K. is subject.

The merger agreement limits O.A.K.'s ability to pursue alternatives to the merger

          The merger agreement contains provisions that limit O.A.K.'s ability to encourage or consider competing third-party proposals to acquire O.A.K., all or a significant part of its stock, or other similar business combinations. These provisions, which include a $3,000,000 termination fee payable under certain circumstances, might discourage a potential competing acquirer that might have an interest in acquiring all or a significant part of O.A.K. from considering or proposing that acquisition even if it were prepared to pay consideration with a higher per share market price than that proposed in the merger, or might result in a potential competing acquirer proposing to pay a

lower per share price to acquire O.A.K. than it might otherwise have proposed to pay. See "Merger Agreement - Termination Fee."

Combining the two companies may be more difficult, costly or time-consuming than we expect

          Chemical and O.A.K. have operated and, until the completion of the merger, will continue to operate independently. It is possible that the integration process could result in the loss of key employees or disruption of each company's ongoing business or inconsistencies in standards, controls, procedures and policies that adversely affect our ability to maintain relationships with customers and employees or to achieve the anticipated benefits of the merger. As with any merger of banking institutions, there also may be business disruptions that cause us to lose customers or cause customers to take their deposits out of our banks. The success of the combined company following the merger may depend in large part on the ability to integrate the two businesses, business models and cultures. If we are not able to integrate our operations successfully and in a timely manner, the expected benefits of the merger may not be realized.

O.A.K. shareholders percentage of ownership of Chemical will be much smaller than their percentage ownership of O.A.K.

          You currently have the right to vote in the election of the board of directors of O.A.K. and on other matters affecting O.A.K. If the merger occurs and you become a shareholder of Chemical, you will have the right to vote in the election of the board of directors of Chemical and on other matters affecting Chemical. However, your percentage ownership of Chemical will be much smaller than your percentage ownership of O.A.K.

Directors and officers of O.A.K. have interests in the merger that differ from the interests of non-director or non-management shareholders

          Some of the directors and officers of O.A.K. have interests in the merger that differ from, or are in addition to, their interests as shareholders of O.A.K., generally. These interests exist because of, among other things, employment or severance agreements that the officers entered into with O.A.K., rights that O.A.K. officers and directors have under O.A.K. benefit plans, and rights to indemnification and directors and officers insurance following the merger. In addition, two of the members of the O.A.K. board of directors will join the board of directors of Chemical. Although the members of each of O.A.K.'s and Chemical's board of directors knew about these additional interests and considered them when they adopted the merger agreement and approved the merger, you should understand that some of the directors and officers of O.A.K. will receive benefits or other payments in connection with the merger that you will not receive. See "The Merger - Interests of O.A.K.'s Directors and Executive Officers in the Merger."

In certain cases, either Chemical or O.A.K. or both may choose to abandon the merger

          In certain cases, such as if the merger is not completed by August 31, 2010, or if one or more events occur that have a material adverse effect on either Chemical or O.A.K., either Chemical or O.A.K., if it is not in breach of its obligations under the merger agreement, may terminate the merger agreement and abandon the merger. For a fuller discussion of the circumstances under which either Chemical or O.A.K. or both may terminate the merger agreement and abandon the merger, see "The Merger Agreement-Termination of the Merger Agreement."

Termination of the merger agreement could negatively impact O.A.K.

          If the merger agreement is terminated, there may be various consequences. For example, O.A.K.'s businesses may have been adversely impacted by the failure to pursue other beneficial opportunities due to the focus of management on the merger, without realizing any of the anticipated benefits of completing the merger, or the market price of O.A.K. common stock could decline to the extent that the current market price reflects a market assumption that the merger will be completed. If the merger agreement is terminated and O.A.K.'s board of directors seeks another merger or business combination, O.A.K.'s shareholders cannot be certain that O.A.K. will be able to find a party willing to pay an equivalent or more attractive price than the price Chemical has agreed to pay in the merger. O.A.K. is required to pay Chemical a $3,000,000 termination fee under certain circumstances.

We may fail to realize the cost savings estimated for the merger

          Chemical estimates to achieve cost savings from the merger when the two companies have been fully integrated. It is possible that these estimates of the potential cost savings could turn out to be incorrect. The cost savings estimates also assume our ability to combine the businesses of Chemical and O.A.K. in a manner that permits those cost savings to be realized. If the estimates turn out to be incorrect or Chemical is not able to combine successfully the two companies, the anticipated cost savings may not be fully realized or realized at all, or may take longer to realize than expected.

The merger consideration is subject to adjustment in certain limited circumstances

          Upon completion of the merger, you will be entitled to receive 1.306 shares of Chemical common stock for each of your shares of O.A.K. common stock. However, the merger consideration is subject to adjustment in certain limited circumstances, including, among others, if the aggregate of certain loan loss and shareholders' equity levels exceed $10,000,000 by an amount up to a maximum of $5,000,000. You can find additional information about potential adjustments to the merger consideration under the heading "The Merger Agreement - Adjustments to the Merger Consideration." If an event occurs that triggers an adjustment to the merger consideration, you could be entitled to receive less shares of Chemical common stock for each of your shares of O.A.K. common stock.

The opinion obtained by O.A.K. from its financial advisor will not reflect subsequent changes

          Donnelly Penman & Partners, the financial advisor to O.A.K., has delivered a "fairness opinion" to the board of directors of O.A.K. The opinion of Donnelly Penman & Partners is directed to the board of directors of O.A.K. and is not a recommendation to any shareholder on how to vote on the merger agreement or any other matter. The opinion, which was originally issued on January 5, 2010, and which was updated as of the date of this document, states that, based upon and subject to the assumptions and limitations on review set forth in the opinion, the terms of the merger are fair, from a financial point of view, to O.A.K. shareholders. The opinion does not reflect changes that may occur or may have occurred after the date of this updated opinion, including changes to the operations and prospects of Chemical or O.A.K., changes in general market and economic conditions, changes in the market price of Chemical common stock, any adjustment to the merger consideration under the merger agreement, or regulatory or other factors. Any such changes, or other factors on which the updated opinion is based, may alter the relative value of Chemical and O.A.K.

The merger may fail to qualify as a reorganization for federal income tax purposes, resulting in your recognition of taxable gain or loss in respect of all of your O.A.K. common stock

          Chemical and O.A.K. intend for the merger to qualify as a reorganization within the meaning of Section 368(a) of the Internal Revenue Code of 1986 (the " Code "). The Internal Revenue Service (the " IRS ") will not provide a ruling on the matter. Chemical and O.A.K. each will, as a condition to closing, obtain an opinion from counsel that the merger will constitute a reorganization for federal income tax purposes. However, these opinions do not bind the IRS or prevent the IRS from adopting a contrary position. If the merger fails to qualify as a reorganization, you generally would recognize gain or loss on each share of O.A.K. common stock surrendered in an amount equal to the difference between your adjusted tax basis in that share and the fair market value of the Chemical common stock received in exchange for that share upon completion of the merger.

A continuation of recent turmoil in the financial markets could have an adverse effect on the financial position or results of operations of Chemical, O.A.K. or the combined company

          In recent periods, United States and global markets, as well as general economic conditions, have been disrupted and volatile. Concerns regarding the financial strength of financial institutions have led to distress in credit markets and issues relating to liquidity among financial institutions. Some financial institutions around the world have failed; others have been forced to seek acquisition partners. The United States and other governments have taken steps to try to stabilize the financial system, including investing in financial institutions. Chemical's and O.A.K.'s businesses and financial condition and results of operations could be adversely affected by (i) continued disruption and volatility in financial markets, (ii) continued capital and liquidity concerns regarding financial institutions generally and our counterparties specifically, (iii) limitations resulting from governmental action in an

effort to stabilize or provide additional regulation of the financial system, or (iv) recessionary conditions that are deeper or last longer than currently anticipated. Further, there can be no assurance that action by Congress, governmental agencies and regulators, including the enacted legislation authorizing the U.S. government to invest in financial institutions, or changes in tax policy, will help stabilize the U.S. financial system and any such action, including changes to existing legislation or policy, could have an adverse effect on the financial position or results of operation of Chemical, O.A.K. or the combined company.

Chemical

          The board of directors of Chemical has unanimously determined that the proposed merger is desirable and in the best interests of its shareholders. In negotiating the terms of the merger agreement and in considering its adoption, the board of directors of Chemical reviewed the financial results and conditions of Chemical and O.A.K., the perceived prospects for each in the future, and the business philosophies of Chemical and O.A.K.

          Chemical's board of directors has recognized that its opportunity to grow organically within its existing markets is, to some degree, limited by competition and economic conditions. Growth through acquisition has been part of Chemical's strategic plan for several years. O.A.K.'s expressed interest in a business combination presented Chemical's board of directors and management with an opportunity to implement this strategy.

          Chemical's management believes that Chemical has the capital and systems capacity to support a larger organization. The strategic combination with O.A.K. is expected to allow Chemical to deploy its capital and systems more efficiently to support a larger organization. Chemical also believes that each organization has complimentary strengths in its product offerings that present opportunities for synergies for both banks when these strengths are shared between the two organizations.

          The board of directors of Chemical believes the merger provides the shareholders of Chemical an opportunity to have an interest in a larger and more diversified financial organization. Shareholders of Chemical may enjoy certain benefits associated with the combined organization's larger and more diversified asset base and access to a broader range of markets. The shareholders of Chemical will, however, be subject to the risks associated with O.A.K., in which they have not previously held an interest.

          The board of directors of Chemical believes that the merger will enable the corporations' subsidiaries to become more effective competitors in their respective markets through access to greater financial and managerial resources. The board of directors of Chemical considers this access to be important in light of increased competition from a broader range of financial institutions than has generally been encountered in the banking industry. The board of directors of Chemical also believes that the merger will permit the achievement of certain economies of scale in the areas of administration, regulatory compliance, management and capital formation. The board of directors of Chemical did not assign any particular weight to any one of the foregoing factors.

Fairness Opinion of Donnelly Penman & Partners

          O.A.K. retained Donnelly Penman to act as O.A.K.'s financial advisor in connection with the merger and related matters based upon its qualifications, expertise and reputation, as well as its familiarity with O.A.K. Donnelly Penman is a recognized investment banking and advisory firm. As a part of its investment banking and advisory business, Donnelly Penman is continually engaged in the valuation of businesses and securities in connection with mergers and acquisitions, secondary distributions of securities, private placements and valuations for ESOP, going private transactions, corporate and other purposes.

          At the January 5, 2010 special meeting of the O.A.K. board of directors (" O.A.K. Board "), Donnelly Penman provided an oral opinion that the exchange ratio of 1.306 shares of Chemical common stock for each share of O.A.K. common stock as described in the merger agreement is fair to O.A.K.'s shareholders from a financial point of view. No limitations were imposed by O.A.K. on the scope of Donnelly Penman's investigation or on the procedures followed by Donnelly Penman in rendering its opinion. At the same meeting, the O.A.K. Board approved the merger and the merger agreement, subject to review by the O.A.K. Board of the final version of certain ancillary agreements. On January 7, 2010, Donnelly Penman delivered its written opinion to the O.A.K. Board confirming its oral opinion, and the O.A.K. Board voted, unanimously, to adopt the plan of merger and recommend that the shareholders of O.A.K. approve the merger agreement.

          The full text of the opinion of Donnelly Penman, which sets forth, among other things, assumptions made, procedures followed, matters considered and limits on the review undertaken by Donnelly Penman, is attached as Appendix B to this prospectus and proxy statement. Holders of O.A.K. common stock are urged to read the opinion in its entirety. Donnelly Penman's opinion is directed only to the merger consideration described in the merger agreement and does not constitute a recommendation to any O.A.K. shareholder as to how such shareholder should vote at the O.A.K. special shareholder meeting. The summary set forth in this prospectus and proxy statement of the opinion of Donnelly Penman is qualified in its entirety by reference to the full text of its opinion attached to this document as Appendix B.

          In arriving at its opinion, Donnelly Penman engaged in discussions with members of both the management teams of O.A.K. and Chemical concerning the historical and current business operations, financial conditions and prospects of O.A.K. and Chemical and reviewed:

independently to verify, such information. Donnelly Penman has further relied upon the assurance of management of O.A.K. and Chemical that they were unaware of any facts that would make the information provided or available to Donnelly Penman incomplete or misleading in any respect. Donnelly Penman did not make any independent evaluations, valuations or appraisals of the assets or liabilities of O.A.K. and Chemical. Donnelly Penman did not review any individual credit files and assumed that the aggregate allowances for credit losses relating to the loans of O.A.K. and Chemical were and will continue to be adequate to cover such losses. The opinion is necessarily based upon economic and market conditions and other circumstances as they existed and were evaluated by Donnelly Penman on the date of its opinion. Donnelly Penman does not have any obligation to update its opinion, unless requested by the O.A.K. Board in writing to do so, and Donnelly Penman expressly disclaims any responsibility to do so in the absence of such a written request.

          No limitations were imposed by O.A.K. on Donnelly Penman on the scope of Donnelly Penman's investigation or the procedures to be followed by Donnelly Penman in rendering its opinion. During the two year period preceding the engagement of Donnelly Penman by O.A.K. with respect to the merger with Chemical, there was no material relationship between Donnelly Penman or any of its affiliates or representatives on the one hand and O.A.K. or any of its affiliates on the other hand, except O.A.K. engaged Donnelly Penman in early 2009 to provide certain financial advisory services for a total fee of $12,500. The form and amount of the consideration to be paid to O.A.K. or its shareholders were determined through arms length negotiations between O.A.K. and Chemical. Donnelly Penman was not requested to opine as to, and its opinion does not address, O.A.K.'s underlying business decision to proceed with or effect the merger or the relative merits of the merger compared to any alternative transaction that might be available to O.A.K. Further, its opinion does not constitute a recommendation to the shareholders of O.A.K. with respect to any approval of the merger agreement or the merger.

          Additionally, Donnelly Penman was not requested to opine as to, and its opinion does not address, the fairness of the amount or nature of the compensation to any of O.A.K.'s officers, directors or employees other than the merger consideration to be received, if any, by such persons due to their status as a shareholder of O.A.K.

          In the analyses, Donnelly Penman has made numerous assumptions with respect to industry performance, business and economic conditions, and other matters, many of which are beyond the control of O.A.K. Any estimates contained in the analyses are not necessarily indicative of future results or value, which may be significantly more or less favorable than such estimates. Estimates of values of companies do not purport to be appraisals or to necessarily reflect the prices at which companies or their securities actually may be sold. No comparable company or merger utilized in our analyses was identical to O.A.K., Chemical or the merger. Accordingly, such analyses are not based solely on arithmetic calculations; rather, they involve complex considerations and judgments concerning differences in financial and operating characteristics of the relevant companies, the timing of the relevant mergers and prospective buyer interests, as well as other factors that could affect the public trading markets of O.A.K. and Chemical or companies to which it is being compared. None of the analyses performed by Donnelly Penman was assigned a greater significance than any other.

          The financial forecast information and projected cost savings and other projected synergies expected to result from the merger furnished by management of O.A.K. and Chemical, respectively, and deemed reasonable by them, contained in or underlying Donnelly Penman's analyses are not necessarily indicative of future results or values, which may be significantly more or less favorable than such forecasts and estimates. The forecasts and estimates were based on numerous variables and assumptions that are inherently uncertain, including factors related to general economic and competitive conditions. In that regard, Donnelly Penman assumed, with O.A.K.'s and Chemical's consent, that the projected financial forecasts, including the projected cost savings, projected ASC 805 adjustments, and other projected synergies expected to result from the merger, were reasonably prepared on a basis reflecting the best currently available judgments of O.A.K. and Chemical, and that such forecasts will be realized in the amounts and at the times that they contemplate. The estimates contained in Donnelly Penman's analyses are not necessarily indicative of actual values or future results, which may be significantly more or less favorable than those suggested by those analyses. Estimates of values of financial institutions or assets do not purport to be appraisals or necessarily reflect the prices at which financial institutions or their securities actually may be sold. Accordingly, actual results could vary significantly from those assumed in the financial forecasts and related analyses.

          The following is a brief summary of the analyses performed by Donnelly Penman in connection with its oral opinion delivered to the O.A.K. Board on January 5, 2010 and with its written opinion delivered to the O.A.K.

Board on January 7, 2010. Certain analyses, herein, have been updated to reflect currently available information for purposes of the written fairness opinion.

Summary Analysis of the Transaction

          Donnelly Penman reviewed the terms of the merger. It noted that the exchange ratio of 1.306 shares of Chemical common stock for each share of O.A.K. common stock meant that the transaction had an implied per share value of $28.65 for each share of O.A.K. common stock based upon the closing price of Chemical of $21.94 on January 6, 2010. This implied per share value represents a 111.2% premium to tangible book value per O.A.K. share of $25.76 as of December 31, 2009. Donnelly Penman also noted that, based on the exchange ratio, the transaction had an implied aggregate value of approximately $77.4 million (exclusive of transaction costs) as of January 6, 2010. The complete aggregate deal metrics are displayed below:

Dividend Analysis

          Donnelly Penman reviewed the current quarterly dividend distribution rates for each company and assumed an annualized rate of each such quarterly distribution rate. Donnelly Penman noted that under current quarterly dividend distribution rates for both companies and taking into account the 1.306 exchange ratio per O.A.K. share that there is a material increase in both the nominal amount of the cash dividend as well as the effective yield for O.A.K. shareholders (after the merger is completed). Donnelly Penman also reviewed a scenario with reduced dividends of 50% for both entities. Under both scenarios, the analysis yielded a higher dividend level to O.A.K. shareholders if the merger was consummated.

Contribution Analysis

          The contribution analysis performed by Donnelly Penman compares the relative contribution of key balance sheet and income statement measures by Chemical and O.A.K. to the pro-forma consolidated company.

O.A.K. / Chemical
Contribution Analysis (1)
($ in 000s)

The range of contribution from O.A.K. ranges from 5.1% to 18.9% in the pro forma consolidated company, with an average of 13.1%. Donnelly Penman notes that O.A.K. shareholders will own 12.9% of the pro forma company.

Analysis of Selected Comparable Companies - Midwest Peer Group - O.A.K.

          Donnelly Penman compared selected financial and operating results of O.A.K. to a peer group that included the following 57 publicly traded commercial banks in Illinois, Indiana, Michigan, Ohio, and Wisconsin, which were selected based on comparable asset size. Specifically, the peer group identified had assets between $400 million and $1.5 billion. The peer group had median trading multiples of 55.15% of book value per share, 67.85% of tangible book value per share and 12.60 times latest twelve months earnings per share. This compares with O.A.K.'s financial metrics of 65.77% book value per share, 65.83% of tangible book value per share and a non-meaningful earnings multiple as of December 31, 2009. These peer companies consisted of: