Important Reactions of
The acrylic and methacrylic esters are interesting chemicals with two reactive sites •—the vinyl and ester groups. Commercially, the reactions of the vinyl groups are the more important. As a site for polymerization reactions, the vinyl group leads to a wide variety of homo- and copolymers with broad ranges of properties. The vinyl group can also undergo ad dition reactions with a variety of reagents, and thus makes these esters valuable chemical interme diates for synthesizing many useful compounds — for example, phar maceuticals, surface-active agents, and photographic developers. Some of the more interesting ad dition reactions of the acrylic and methacrylic esters are given here.
ACRYLIC
mmrn
ROHM & HAAS ACRYLIC MONOMERS
methyl acrylate ethyl acrylate butyl acrylate 2-ethylhexyl acrylate methyl methacrylate ethyl methacrylate glacial
butyl methacrylate hexyl methacrylate decyl-octyl methacrylate lauryl methacrylate stearyl methacrylate glacial methacrylic acid acrylic acid
• R e a c t i o n s w i t h D i e n e s . Acrylic esters and acids readily undergo the Diels-Alder reaction with dienes to form alicyclic and heterocyclic esters and acids. This reaction can be carried out with aliphatic and alicyclic 1,3-dienes; certain aromatic compounds, such as anthracene; conjugated heterocyclic compounds; dienes con taining elements other than carbon as part of the conjugated system, such as acrolein; and conjugated dienoic fatty acids or their parent oils. CH2 CH2 / \ // CH CH- COOCH3 CH CH- COOCH3
1
+
CH
II
CH2
^N
CH2 butadiene
^
meth acrylate methyl
CH CH2 V CH2 methyl tetrahydrobenzoate
Reactions with Active Hydrogen Compounds.
a. A d d i t i o n o f S u l f u r C o m p o u n d s — Mercaptans add readily to both acrylic and methacrylic esters to give excellent yields of sulfides, in the presence of a basic catalyst. R'
R' base RSH + CH2=C—COOR" -• R—S—CH2CHCOOR" (R'=H or CH3) Reactions of H2S, thiolic acids, and sodium tetrasulfide with specific acrylates and methacrylates have also been investigated. H2S + 2CH2=CHCOOCH3 • CH3OOCCH2CH2—S—CH2CH2COOCH3 methyl acrylate dimethyl β-thiodipropionate 26 A
INDUSTRIAL AND ENGINEERING CHEMISTRY
b. A d d i t i o n Of A m m o n i a a n d A m i n e s —An extensive number of reactions of acrylic esters with ammonia and with aliphatic, heterocyclic, and aromatic amines is given in chemical literature. (CH3)2NH + CH2=CHCOOC2H5 dimethylamine ethyl acrylate
• (CH3)2NCH2CH2COOC2H5 ethyl β- (N-dimethylamino) propionate
C. A d d i t i o n o f H a l o g e n A c i d s — T h e addition of HBr to both acrylic and methacrylic esters proceeds readily to give high yields of the corresponding /3-bromopropionates and /3-bromoisobutyrates. These /3-halo esters undergo typical halogen reactions and therefore serve as useful intermediates for products which cannot be obtained readily by direct reaction with an acrylic or methacrylic ester. HBr + CH2=CHCOOC2H5 ethyl acrylate
•
BrCH2CH2COOC2H5 ethyl β-bromopropionate
d. A d d i t i o n o f A l c o h o l s a n d P h e n o l s —Primary and secondary alcohols undergo addition to acrylic esters, with a sodium alkoxide catalyst, to give /3-alkoxypropionates. The reaction with phenols yields β-phenoxypropionates. NaOR ROH + CH2=CHCOOR' • ROCH2CH2COOR' e . A d d i t i o n o f H y d r o g e n C y a n i d e — H y d r o g e n cyanide can be added readily to both acrylic and methacrylic esters in the presence of cyanide or carbonate catalysts at elevated temperatures to give the corresponding /3-cyanopropionates or /3-cyanoisobutyrates. R' R' HCN + CH2=C—COOR"
-•
NCCH2CHCOOR" (R'=H or CH3)
• A d d i t i o n Of N i t r o p a r a f f i n s . Acrylic esters react with nitroparaffins in the presence of basic cata lysts to give nitro esters. A long list of reactions involving many types of nitroparaffins has been reported in the literature. N0 2 (C2H5)3N | CH3CH2N02 + CH2=CHCOOCH3 • CH3CHCH2CH2COOCH3 nitroethane methyl acrylate methyl y-nitrovalerate • O'XO R e a c t i o n . An aldehyde-ester OHCCH2CH2COOR can be prepared from either methyl acrylate or ethyl acrylate by the Oxo process. CH2=CHCOOR + CO + H2
•
OHCCH2CH2COOR
• A d d i t i o n o f H a l o g e n s . Halogens may be added to acrylic and methacrylic esters to give the corresponding a,j9-dihalopropionate and α,/3-dihaloisobutyrate esters. Br2 + CH2=CHCOOCH3
•
CH2 —CHCOOCH3
I
I
Br Br methyl α,β-dibromopropionate
&» L I T E R A T U R E a n d S A M P L E S For more information on these and many other reactions, write t o Dept. SP-1. Monomer samples, and literature on polymerization applications are also available.
Chemicals for Industry
ROHM & HAAS C O M P A N Y WASHINGTON SQUARE, PHILADELPHIA 5, PA.
Circle No. 9 on Readers' Service Card VOL. 5 2 , N O . 7
·
JULY 1960
27A
