Chemistry Reference
In-Depth Information
Many other esters of cellulose were prepared at various times, including some mixed esters.
Various cellulose acetate-butyrates are manufactured today and are perhaps the best known of the
mixed esters. They are synthesized in the same manner as cellulose acetate. Mixed anhydrides are
used in esterification reactions catalyzed by sulfuric acid. The products are then slightly hydrolyzed.
The butyric groups enhance flexibility and moisture resistance. The materials have the reputation of
being tough plastics and are used in such applications as tool handles. Lower molecular weight grades
are also used in surface finishes.
Several
cellulose ethers
are also prepared commercially. The original patents for preparation of
cellulose ethers date from 1912. In spite of that, cellulose ethers never attained the industrial
importance of cellulose esters. The ethers are prepared by reacting alkali cellulose with an alkyl
halide or with an epoxide:
OH
OH
HO
HO
C
2
H
5
Cl
NaOH
O
O
O
O
n
n
OH
Na
OH
HO
O
O
n
OC
2
H
5
OH
O
HO
OH
OH
O
O
O
HO
HO
O
O
O
O
O
O
OH
n
ONa
O
CH
2
OH
Typical commercial ethers are methyl, ethyl, hydroxyethyl, hydroxypropyl, carboxy-methyl,
aminoethyl, and benzyl.
Ethyl cellulose is used industrially as a plastic similarly to cellulose acetate. The water-soluble
ethers, like methyl, carboxymethyl, and hydroxyethyl, are used as thickeners in foods and in paper
manufacturing.
Cellulose can be reacted with acrylonitrile to form a cyanoethylether. The Michael condensation
takes place with alkali cellulose:
N
ONa
O
HO
HO
O
N
O
O
n
O
ONa
n
O
N
