<PAGE>

                                                                EXHIBIT 10.9

                           INTEREST PURCHASE AGREEMENT

      This INTEREST PURCHASE AGREEMENT (this "Agreement") is dated as of
December 20, 1999, by and between PaperExchange.com, LLC, a Delaware limited
liability company (the "Company"), and Kent A. Dolby (the "Holder").

      WHEREAS, the Company wishes to sell and the Holder wishes to buy certain
ownership interests in the Company on the terms and subject to the restrictions
contained in this Agreement.

      NOW, THEREFORE, in consideration of the mutual promises and agreements set
forth herein, the Company and the Holder agree as follows:

      1. DEFINITIONS. As used herein, the following terms shall have the
meanings specified below:

      "Act" has the meaning set forth in Section 4(a) hereof.

      "Balance Sheet" means the balance sheet of the Company dated as of
December 31, 1998.

      "Company" has the meaning set forth in the preamble hereto.

      "Employment Agreement" means the Employment Agreement of even date
herewith between the Company and the Holder.

      "Financial Statements" means the unaudited financial statements of the
Company for the period commencing on April 10, 1998 and ending on December 31,
1998.

      "Fully-Diluted Basis" means the calculation of all of the issued and
outstanding equity interests in the Company after giving effect to the exercise
of all Warrants.

      "Holder" has the meaning set forth in the introductory paragraph hereof.

      "Imputed Rate" means the applicable Federal rate as defined under Section
1274(d) of the Internal Revenue Code of 1986, as amended.

      "Interest Price" means $2.38284 per Membership Interest.

      "Interests" means the Membership Interests of the Company issued to the
Holder pursuant to the terms hereof, and any other units or securities of a
successor entity issued to the Holder pursuant to any recapitalization,
reorganization, or merger of the Company, including in connection with a
Reorganization.

      "Management Board" means the management board of the Company or, in the
event of a Reorganization, any other similar managing body of the successor
entity.
<PAGE>
                                      -2-


      "Membership Interest" has the meaning set forth in the Operating
Agreement.

      "Note" has the meaning set forth in Section 2 hereof.

      "Operating Agreement" means the Company's Amended and Restated Operating
Agreement, dated as of June 1, 1999, among the Company and its members, as
amended by the Amendment to the Amended and Restated Operating Agreement, dated
as of August 26, 1999, and the Second Amendment to the Amended and Restated
Operating Agreement, dated as of November 23, 1999, and, after the date hereof,
the Operating Agreement Amendment, all as further amended from time to time.

      "Operating Agreement Amendment" has the meaning set forth in Section 2
hereof.

      "Option Agreement" means the Equity Option Agreement of even date herewith
between the Company and the Holder.

      "Percentage Interest" has the meaning set forth in the Operating
Agreement.

      "Purchase Price" has the meaning set forth in Section 2 hereof.

      "Reorganization" means the reorganization or conversion of the Company
from a limited liability company into any other form of entity, including any
such reorganization effected by way of merger or transfer of all or
substantially all of the assets or Membership Interests and Economic Interests
(as such term is defined in the Operating Agreement) of the Company to a
corporation or other entity formed at the direction of the Management Board for
purposes of such reorganization.

      "Transfer" has the meaning ascribed to such term in Section 7 of the
Operating Agreement.

      "Warrants" means those certain warrants to purchase equity interests of
the Company issued on October 15, 1999, as reflected in the chart in Section
2.2(e) hereof.

      2. PURCHASE AND SALE OF INTERESTS.

      2.1 Subject to the terms and conditions hereinafter set forth and in
reliance on the representations and warranties contained herein, the Company
hereby issues and sells to the Holder and the Holder hereby purchases from the
Company, on the date hereof, 441,754 Interests. If all of the Employee's options
were exercised pursuant to the Option Agreement, the Interests would represent a
one percent (1%) Percentage Interest in the Company calculated as of the date
hereof on a Fully-Diluted Basis. The aggregate purchase price paid by the Holder
for the Interests will be $1,052,632 (the "Purchase Price"). On the date hereof
(a) the full amount of the Purchase Price will be paid to the Company by
delivery of the Holder's promissory note to the Company in an aggregate
principal amount equal to the Purchase Price and in the form of Exhibit A hereto
(the "Note"), (b) the Operating Agreement shall be amended to reflect the
Holder's purchase of the Interests hereunder and the Holder's admission as a
Member of the Company, in accordance with that certain amendment to the
Operating Agreement to be executed by the Company and each of the Members in the
form of Exhibit B attached hereto (the "Operating Agreement Amendment"), (c) the
Holder shall execute the

<PAGE>
                                      -3-


Irrevocable Voting Proxy of even date herewith in favor of Robert K. Kraft, and
(d) the Holder will deliver to and pledge all of the Interests to the Company
pursuant to the terms of the Note (including without limitation executing UCC-1
financing statements in connection with the Note), together with appropriate
instruments of assignment thereof reasonably acceptable to, and duly executed in
blank by, the Holder.

      2.2 Representations and Warranties of the Company. The Company represents
and warrants as follows:

            (a) After giving effect to the purchase and sale effected hereby the
Interests will be duly authorized and validly issued in compliance with the
Certificate of Formation of the Company and the Operating Agreement.

            (b) The Company is a limited liability company organized, validly
subsisting and in good standing under the laws of Delaware. The Company has all
necessary corporate power, authority and capacity to own its properties and
assets and to carry on its business. The Company has full right, power, capacity
and authority to enter into and perform its obligations under this Agreement,
the Employment Agreement and the Option Agreement. Copies of the certificate of
formation and Operating Agreement of the Company including all amendments
thereto and restatements thereof are annexed as Schedule 1.

            (c) The entering into, execution and delivery by the Company of this
Agreement, the Employment Agreement and the Option Agreement, and the other
agreements contemplated herein to which it is a party, has been duly authorized
by all necessary action on behalf of the Company. This Agreement and the
Employment Agreement have been duly executed and delivered by the Company. This
Agreement, the Employment Agreement and the Option Agreement constitute the
legal, valid, and binding obligation of the Company enforceable against it in
accordance with their terms (subject, as to the enforcement of remedies, to
bankruptcy, reorganization, insolvency, moratorium, and other laws relating to
or affecting creditors' rights generally and subject to the availability of
equitable remedies). Neither the execution and delivery of this Agreement, nor
the Employment Agreement, nor the Option Agreement, nor the performance by the
Company of its obligations hereunder or thereunder will conflict with, or, to
the Company's knowledge, result in a breach of the terms, conditions or
provisions of, or constitute a default under, or result in any violation of, the
laws applicable to the Company, any judgment, order, writ, injunction or decree
of any governmental or regulatory authority, the organizational documents of the
Company, or the provisions of any agreement, arrangement or understanding to
which the Company is a party or by which it, its business or its assets and
properties are bound or affected.

            (d) To the Company's knowledge, it holds all material licenses,
permits and authorizations necessary for the lawful operation of its business
pursuant to all applicable statutes, laws, ordinances, rules and regulations of
all authorities having jurisdiction over the Company or over any part of the
business. To the Company's knowledge, it is not in violation of any laws or
regulations concerning its business, except for violations that are immaterial
to the condition and operation of the business.

            (e) On closing of the Holder's purchase of the Interests after
giving effect to the transactions contemplated hereby, the ownership of the
Company on a Fully-Diluted Basis will be as follows:

<PAGE>
                                      -4-

--------------------------------------------------------------------------------
                        MEMBERSHIP       WARRANTS                       DILUTED
                        INTERESTS        @$2/SHARE         TOTAL       OWNERSHIP
--------------------------------------------------------------------------------
Kraft Group LLC         22,026,000       2,979,168      25,005,168     58.96268%
--------------------------------------------------------------------------------
Internet Capital        9,457,320        1,279,167      10,736,487     25.31685%
Group (PE.com
Holdings)
--------------------------------------------------------------------------------
Terrapin Partners LLC   2,495,253        337,500        2,832,753      6.67969%
--------------------------------------------------------------------------------
Hilton Plein            1,109,001        150,000        1,259,001      2.96875%
--------------------------------------------------------------------------------
Roger Stone             1,109,001        150,000        1,259,001      2.96875%
--------------------------------------------------------------------------------
M&M Kaplan              369,669          50,001         419,670        0.98959%
--------------------------------------------------------------------------------
L Stone                 184,833          24,999         209,832        0.49478%
--------------------------------------------------------------------------------
J Stone                 184,833          24,999         209,832        0.49478%
--------------------------------------------------------------------------------
Steve Kaplan            30,804           4,167          34,971         0.08246%
--------------------------------------------------------------------------------
Kent A. Dolby           441,754                         441,754        1.04167%
--------------------------------------------------------------------------------

--------------------------------------------------------------------------------
TOTAL SHARES
OUTSTANDING             37,408,468       5,000,001       42,408,469     100%
--------------------------------------------------------------------------------

      Except as set forth on Schedule 2 attached hereto, and except as set forth
immediately above, there are no outstanding securities convertible into or
exchangeable or exercisable for any Membership Interests or Economic Interests
in the Company, nor does the Company have outstanding any rights to subscribe
for or to purchase, or any options for the purchase of, or any agreements
providing for the issuance of, any Membership Interests or Economic Interests in
the Company or any securities convertible into or exchangeable or exercisable
for any Membership Interests or Economic Interests in the Company.

            (f) The Financial Statements have been prepared in accordance with
generally accepted accounting principles, consistently applied. The Balance
Sheet presents fairly a true and complete statement in all material respects of
the financial condition, assets and properties and liabilities of the Company as
at December 31, 1998 and the related income statements forming a part of the
Financial Statements accurately sets forth in all material respects the results
of the operations of the Company throughout the period covered thereby. The
Financial Statements do not contain any extraordinary items or items of special
or nonrecurring income or any other income not earned in the ordinary course of
business, except as expressly specified therein.

            (g) To the Company's knowledge, since the date of the Balance Sheet,
there has not been any event or events, alone or in the aggregate, having a
material adverse affect on the Company (excluding general economic conditions).

      3. RESTRICTIONS ON TRANSFER. The Holder agrees (i) to be bound by the
transfer restrictions set forth in the Operating Agreement, and (ii) to execute
the Operating Agreement Amendment simultaneously with the purchase of the
Interests hereunder. Upon the Transfer by the Holder of all or any portion of
the Interests, other than pursuant to any

<PAGE>
                                      -5-


Reorganization or in connection with permitted assignments under the terms of
the Operating Agreement, the Note shall become immediately due and payable. The
Holder agrees that in connection with any Reorganization the Holder shall upon
request of the Management Board execute documents required to effect such
Reorganization, including documents evidencing the Holder's agreement to comply
with any restrictions imposed by the Management Board generally upon all of the
holders (other than Kraft, PE.com Holdings LLC ("PEH"), or any transferees or
assignees of Kraft or PEH) of Membership Interests (or the capital stock or
other securities received in exchange for Membership Interests (or into which
Membership Interests are converted) in a Reorganization) with respect to the
Transfer or voting thereof. The Holder understands and agrees that this
constitutes an irrevocable commitment which the Holder shall not have the right
to cancel or veto.

      4. INVESTMENT REPRESENTATIONS.

      (a) The Holder represents that the Interests are being acquired by him for
his own account for investment and not with a view to the distribution thereof.
The Holder understands that the Interests have not been registered under the
Securities Act of 1933, as amended (the "Act"), on the grounds that the offer
and sale of the Interests to him are exempt from the registration requirements
of the Act under Section 4(2) thereof as a transaction not involving any public
offering of the Interests. The Holder understands that the Company's reliance on
such exemption is predicated in part on the representations of the Holder which
are contained herein.

      (b) The Holder understands that he must bear the economic risk of his
investment in the Interests for an indefinite period of time because the
Interests have not been registered under the Act and, therefore, cannot be sold
unless they are subsequently registered under the Act or an exemption from such
registration is available. The Holder agrees that he will not offer to Transfer
any of the Interests except as expressly permitted by the Operating Agreement
and this Agreement and then only after the Company has received an opinion of
counsel that such offer or Transfer is not in violation of the registration
requirements of the Securities Act of 1933, as amended, or other applicable law.

      (c) The Holder represents that he is a resident of the Commonwealth of
Pennsylvania.

      (d) The Holder represents and confirms that he has had an opportunity to
obtain information concerning the Company as desired to evaluate the merits and
risks in holding the Interests, and the Holder is not relying on any statement,
representation or warranty made by the Company or any person except for the
representations and warranties of the Company set forth in this Agreement.

      5. GENERAL.

      5.1. Notices. All notices, demands and other communications hereunder
shall be in writing or by written telecommunication, and shall be deemed to have
been duly given if delivered personally or if mailed by certified mail, return
receipt requested, postage prepaid, or if sent by overnight courier, or sent by
written telecommunication, as follows:

<PAGE>
                                      -6-


      If to the Company, to:

            PaperExchange.com, LLC
            545 Boylston Street
            Boston, Massachusetts 02108
            Attention: Chairman

      With a copy sent contemporaneously to:

            Jonathan K. Bernstein, Esq.
            Bingham Dana LLP
            150 Federal Street
            Boston, Massachusetts 02110

      If to the Holder, to:

            Kent A. Dolby
            632 Olympia Hills Circle
            Berwyn, Pennsylvania 19312

      With a copy sent contemporaneously to:

            Michael A. Schlesinger, Esq.
            Tucker Flyer
            1615 L Street, N.W.
            Suite 400
            Washington, D.C. 20036

      Any such notice shall be effective (a) if delivered personally, when
received, (b) if sent by overnight courier, when receipted for, (c) if mailed,
three (3) days after being mailed as described above, and (d) if sent by written
telecommunication, when dispatched.

      5.2. Equitable Remedies. Each of the parties hereto acknowledges and
agrees that upon any breach by the Holder of his obligations under Section 3
hereof, the Company will have no adequate remedy at law, and accordingly will be
entitled to specific performance and other appropriate injunctive and equitable
relief.

      5.3. Severability. If any provision of this Agreement is or becomes
invalid, illegal or unenforceable in any respect under any law, the validity,
legality and enforceability of the remaining provisions hereof shall not in any
way be affected or impaired.

      5.4. Waivers. No delay or omission by either party hereto in exercising
any right, power or privilege hereunder shall impair such right, power or
privilege, nor shall any single or partial exercise of any such right, power or
privilege preclude any further exercise thereof or the exercise of any other
right, power or privilege.

      5.5. Counterparts. This Agreement may be executed in multiple
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

<PAGE>
                                      -7-


      5.6. Assigns. This Agreement shall not be assignable or transferable by
the Holder without the Company's prior written consent thereto. Any
Reorganization will require that, at closing thereon, this Agreement, the
Employment Agreement and the Option Agreement, and all of the Company's
obligations hereunder and thereunder, are fully assumed by the Company's
transferee or successor in interest.

      5.7. Entire Agreement. This Agreement contains the entire understanding of
the parties, supersedes all prior agreements and understandings relating to the
subject matter hereof and shall not be amended except by a written instrument
hereafter signed by each of the parties hereto. Nothing in this Agreement shall
be construed as a grant to the Holder of any right to continuing employment with
the Company or to restrict in any way the right to terminate the Holder's
employment at any time.

      5.8. Governing Law. This Agreement and the obligations of the parties
hereunder shall be deemed to be a contract under seal and shall for all purposes
be governed by and construed in accordance with the internal laws of the State
of Delaware without reference to principles of conflicts of law.

      5.9 Consent to Jurisdiction, Counsel. The Holder agrees that the courts of
the Commonwealth of Massachusetts and the United States District Court for the
District of Massachusetts shall have exclusive jurisdiction to hear and
determine any claims or disputes between or among the Holder and any person or
entity (including, without limitation, the Company) pertaining directly or
indirectly to this Agreement or to any matter arising hereunder. The Holder
expressly submits and consents in advance to such jurisdiction in any action or
proceeding commenced in such courts, hereby waiving personal service of the
summons and complaint, or other process or papers issued therein, and agreeing
that service of such summons and complaint, or other process or papers, may be
made by registered or certified mail addressed to the Holder at the address set
forth herein. The Holder acknowledges that he has carefully read this Agreement
and that he has had an opportunity to consult with an attorney of its own
selection before signing it and he understands the effects of this Agreement and
is signing it voluntarily

      5.10. Construction. The language used in this Agreement will be deemed to
be the language chosen by the parties to express their mutual intent, and no
rule of strict construction will be applied against any party.

      5.11. Waiver of Jury Trial. EACH PARTY HERETO WAIVES ITS RIGHTS TO A JURY
TRIAL WITH RESPECT TO ANY ACTION OR CLAIM ARISING OUT OF ANY DISPUTE IN
CONNECTION WITH THIS AGREEMENT, ANY AGREEMENT, CONTRACT OR OTHER DOCUMENT OR
INSTRUMENT EXECUTED IN CONNECTION HEREWITH, OR ANY OF THE TRANSACTIONS
CONTEMPLATED HEREBY.

                           [Execution page to follow.]

<PAGE>

      IN WITNESS WHEREOF, and intending to be legally bound hereby, the parties
hereto have caused this Agreement to be duly executed as of the date and year
first above written.

THE COMPANY:                        PAPEREXCHANGE.COM, LLC


                                    By: /s/ Robert K. Kraft
                                        ------------------------
                                        Name:   Robert K. Kraft
                                        Title:  Chairman


THE HOLDER:

                                    /s/ Kent A. Dolby
                                    ----------------------------
                                    Kent A. Dolby

<PAGE>

                                   SCHEDULE 1

                     Formation and Organizational Documents
<PAGE>

                                   SCHEDULE 2

                   Outstanding Rights to Purchase or Subscribe

o     Two (2) Employees are permitted to purchase an aggregate maximum of
      $200,000 of restricted equity in the Company in connection with an IPO.

o     Outstanding options granted pursuant to the Company's 1998 Equity Option
      Plan, as amended, to purchase an aggregate of 2,757,248 Economic Interests
      of the Company.
<PAGE>

                                    EXHIBIT A

                                  Form of Note
<PAGE>

                                    EXHIBIT B

                          Operating Agreement Amendment