EXHIBIT 4.16

                                      A-1

                         [FORM OF FRONT OF DEBENTURE]

No.                                                             $

                             ARCO CHEMICAL COMPANY

               10.25% Debenture Due 2010        CUSIP 


        ARCO CHEMICAL COMPANY, a corporation duly organized and existing under 
the laws of the State of Delaware (herein called the "Company"), for value 
received, hereby promises to pay to
                                   or registered assigns, the principal sum of
                                   Dollars at the office or agency of the 
Company in the Borough of Manhattan, The City of New York, on November 1, 2010
(the "Maturity Date"), in such coin or currency of the United States of America
as at the time of payment shall be legal tender for the payment of public and
private debts, and to pay interest, semi-annually on May 1 and November 1 of
each year (each an "Interest Payment Date"), commencing with the Interest
Payment Date next following November 7, 1990 (the "Original Issue Date"), and
on the Maturity Date, on said principal sum at said office or agency, in like
coin or currency, at the rate per annum specified in the title hereof, from the
May 1 or November 1, as the case may be, to which interest on this Debenture
has been paid next preceding the applicable Interest Payment Date or, if no
interest has been paid on this Debenture, from the Original Issue Date until
payment of said principal sum has been made or duly provided for; provided,
however, that any payment of principal or interest to be made on an Interest
Payment Date or Maturity Date which is not a Business Day shall be made on the
next succeeding Business Day with the same force and effect as if made on the
Interest Payment Date or Maturity Date, as the case may be, and no additional
interest shall accrue as a result of such delayed payment. For purposes of this
Debenture, "Business Day" means any day, other than a Saturday or Sunday, that
is not a day on which banking institutions are authorized or required by law or
regulation to be closed in The City of New York or The City of Philadelphia. The
interest so payable on any Interest Payment Date or the Maturity Date will,
except as provided in the Indenture, be paid to the person in whose name the
Debenture is registered at the close of business on the April 15 or October 15
next preceding such Interest Payment Date (a "Record Date") in the case of
interest payments on other than the Maturity Date, and on the Maturity Date in
the case of an interest payment on the Maturity Date, whether or not such
fifteenth day or Maturity Date is a Business Day. At the option of the Company,
interest so payable may be paid by check mailed to the registered address of
such person; provided that, if the holder hereof is the holder of U.S.
$10,000,000 or more in aggregate principal amount


 
                                      A-2

of Debentures, such payments will be made by wire transfer of immediately 
available funds, but only if appropriate wire transfer instructions have been 
received in writing by the Trustee not less than fifteen days prior to the 
applicable Interest Payment Date. Principal and interest payable at maturity in 
respect of this Debenture will be paid in immediately available funds upon 
surrender of this Debenture.

        Interest will be computed on the basis of a 360-day year of twelve 
30-day months.

        All payments of principal and interest in respect of this Debenture will
be made net of any deduction or withholding for or on account of all taxes, 
duties, assessments or governmental charges of whatever nature imposed or levied
by or on behalf of any governmental authority if the Company is required by law 
to deduct or withhold amounts for or on account of such taxes, duties, 
assessments or governmental charges.

        Reference is made to the further provisions of this Debenture set forth 
on the reverse hereof. Such further provisions shall for all purposes have the 
same effect as though fully set forth at this place.

        This Debenture shall not be valid or become obligatory for any purpose 
until the certificate of authentication hereon shall have been signed by the 
Trustee under the Indenture referred to on the reverse hereof.

 
                                      A-3

        IN WITNESS WHEREOF, ARCO Chemical Company has caused this Debenture to 
be signed, manually or by facsimile, by its President and Chief Executive 
Officer and by its Vice President and Treasurer, under its corporate seal (which
may be printed, engraved or otherwise reproduced thereon by facsimile or 
otherwise).

        Dated:

                                        ARCO CHEMICAL COMPANY


Attest:                                 By
                                          --------------------------------------
                                          President and Chief Executive Officer


By
   ----------------------------------
     Vice President and Treasurer

[SEAL]


                   [TRUSTEE'S CERTIFICATE OF AUTHENTICATION]


        This is one of the Securities issued under the within mentioned 
Indenture.

                                        THE BANK OF NEW YORK
                                          as Trustee

                                        
                                        By
                                          --------------------------------------
                                                   Authorized Signatory


 
                                      A-4

                         [FORM OF REVERSE OF DEBENTURE]

                             ARCO CHEMICAL COMPANY

                           10.25% DEBENTURE DUE 2010

        This Debenture is one of a duly authorized issue of debentures, notes, 
bonds or other evidences of indebtedness of the Company (herein called the 
"Securities") of the series hereinafter specified, all issued or to be issued 
under and pursuant to an Indenture dated as of June 15, 1988 (herein called the 
"Indenture"), duly executed and delivered by the Company to The Bank of New 
York, Trustee (hereinafter called the "Trustee"), to which Indenture and all 
indentures supplemental thereto reference is hereby made for a description of 
the rights, limitation of rights, obligations, duties and immunities thereunder 
of the Trustee, the Company and the Holders of the Securities. The Securities 
may be issued in one or more series, which different series may be issued in 
various aggregate principal amounts, may mature at different times, may bear 
interest (if any) at different rates, may be subject to different redemption 
provisions (if any), may be subject to different sinking, purchase or analogous 
funds (if any), may be subject to different covenants and Events of Default and 
may otherwise vary as provided in the Indenture.

        This Debenture is one of a series of Securities of the Company issued 
pursuant to the Indenture designated as the 10.25% Debentures Due 2010 (herein 
called the "Debentures") limited in aggregate principal amount to $100,000,000.

        In case an Event of Default shall occur and be continuing, the principal
hereof may be declared, and upon such declaration shall become, due and payable,
in the manner, with the effect and subject to the conditions provided in the 
Indenture.

        The Indenture contains provisions permitting the Company and the 
Trustee, with the consent of the Holders of not less than 50% in aggregate 
principal amount at Stated Maturity of the Securities at the time outstanding of
each series affected by such supplemental indenture or indentures, evidenced as 
provided in the Indenture, to execute supplemental indentures adding any 
provisions to or changing in any manner or eliminating any of the provisions of 
the Indenture or any supplemental indenture as such provisions apply to such 
Securities or modifying in any manner the rights of the Holders of the 
Securities; provided, however, that no such supplemental indenture shall (i) 
extend the fixed maturity of any Security or reduce the rate of interest or 
extend the time of payment of

 
                                      A-5

interest thereon or reduce the principal thereof or the time during which 
premium is payable thereon or change the method of computing the amount of 
principal thereof or make the principal thereof or any premium or interest 
thereon payable in any coin or currency other than that provided in the 
Securities or reduce the amount of the principal of an Original Issue Discount 
Security that would be due and payable upon an acceleration of the maturity 
thereof or the amount thereof provable in bankruptcy without the consent of the 
Holder thereof, or (ii) reduce the percentage in principal amount at Stated 
Maturity of the outstanding Securities, the consent of whose Holders is required
for any such supplemental indenture, or the consent of whose Holders is required
for any waiver of compliance with certain provisions of the Indenture or of 
certain defaults under, and their consequences provided for in, the Indenture, 
without the consent of the Holders of each Security of such series so affected. 
Any such consent or waiver by the Holder of this Debenture (unless revoked as 
provided in the Indenture) shall be conclusive and binding upon such Holder and 
upon all future Holders and owners of this Debenture and any Debentures which 
may be issued in exchange or substitution herefor, irrespective of whether or 
not any notation thereof is made upon this Debenture or such other Debentures.

        No reference herein to the Indenture and no provision of this Debenture 
or of the Indenture shall alter or impair the obligation of the Company, which 
is absolute and unconditional, to pay the principal of and interest on this 
Debenture at the place, at the respective times, at the rate and in the coin or 
currency herein prescribed.

        The Debentures are issuable in registered form without coupons in 
denominations of $1,000 and integral multiples thereof. Debentures may be 
exchanged for a like aggregate principal amount of Debentures of other 
authorized denominations, without charge except for any tax or other 
governmental charge imposed in relation thereto, at the office or agency of the 
Company in the Borough of Manhattan, The City of New York, and in the manner and
subject to the limitations provided in the Indenture.

        The Debentures are unsecured obligations of the Company ranking pari 
passu without any preference among themselves and equally with all other 
unsecured indebtedness (other than subordinated indebtedness) of the Company 
from time to time outstanding.

        The Debentures are not redeemable on any date prior to maturity.

 
                                      A-6

        Upon due presentment for registraton of transfer of this Debenture at 
the office or agency of the Company in the Borough of Manhattan, The City of New
York, a new Debenture or Debentures of authorized denominations for an equal 
aggregate principal amount at Stated Maturity will be issued to the transferee 
in exchange therefor, subject to the limitations provided in the Indenture, 
without charge except for any tax or other governmental charge imposed in 
relation thereto.

        Prior to due presentment for registration of transfer of the Debenture, 
the Company, the Trustee, any paying agent and any Debenture registrar may deem 
and treat the registered Holder hereof as the absolute owner of this Debenture 
(whether or not this Debenture shall be overdue and notwithstanding any notation
of ownership or other writing hereon by anyone other than the Company, any 
Debenture registrar or the Trustee), for the purpose of receiving payment hereof
or on account hereof, and for all other purposes (subject to the provisions 
appearing on the face hereof), and neither the Company nor the Trustee nor any 
paying agent nor any Debenture registrar shall be affected by any notice to the 
contrary.

        No recourse for the payment of the principal of or interest on this 
Debenture, or for any claim based hereon or otherwise in respect hereof, and no 
recourse under or upon any obligation, covenant or agreement of the Company in 
the Indenture or any indenture supplemental thereto or in any Debenture, or 
because of the creation of any indebtedness represented thereby, shall be had 
against any incorporator, stockholder, officer or director, as such, past, 
present or future, of the Company or any successor corporation, whether by 
virtue of any constitution, statute or rule or law or by the enforcement of any 
assessment or penalty or otherwise, all such liability being, by the acceptance 
hereof and as a condition of and as part of the consideration for the issue 
hereof, expressly waived and released.

        Terms used herein which are not defined herein shall have the meanings 
assigned to them in the Indenture.

        This Debenture shall be governed by and construed in accordance with the
laws of the State of New York.

 
                                      A-7

        The following abbreviations, when used in the inscription on the face of
the within instrument, shall be construed as though they were written out in 
full according to applicable laws or regulations:

TEN COM --as tenants in common                                  Custodian
TEN ENT --as tenants by the             UNIF GIFT MIN ACT -- ---------------
          entireties                                          (Cust) (Minor)
JT TEN  --as joint tenants with right   under Uniform Gifts to Minors Act
          of survivorship and not as
          tenants in common             ------------------------------------  
                                                       (State)

        Additional abbreviations may also be used though not in the above list.

                                ---------------

        FOR VALUE RECEIVED the undersigned hereby sell(s), assigns(s) and 
transfer(s) unto

PLEASE INSERT SOCIAL SECURITY OR OTHER
   IDENTIFYING NUMBER OF ASSIGNEE


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              (NAME AND ADDRESS OF ASSIGNEE, INCLUDING ZIP CODE, 
                        MUST BE PRINTED OR TYPEWRITTEN)


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the within Debenture, and all rights thereunder, hereby irrevocably constituting
and appointing

                                                                        attorney
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to transfer such Debenture in the books of the Company, with full power of 
substitution in the premises.

        Dated:
                                                --------------------------------

        NOTICE: The signature to this assignment must correspond with the name 
as written upon the face of the within instrument in every particular, without 
alteration or enlargement or any change whatever.