Page 25 - Academic Press Encyclopedia of Physical Science and Technology 3rd Organic Chemistry

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Encyclopedia of Physical Science and Technology EN001F-4 May 7, 2001 16:19

Acetylene 77

FIGURE 11 Vitamin A production. Reaction flow sheet (steps 15–18): C 14 aldehyde → vitamin A sequence.

salts in the presence of base undergo rapid elimination to A. Barban
phosphoranes (ylides), which react readily with carbonyl
SOCl 2 or PCl 3
compounds to form olefins to high yield. By a repetition HO CH 2 C C CH 2 OH
of this sequence the carbon chain is built up to that of
(A) Cl CH 2 C C CH 2 OH
retinol.
HCl
NH 2 COCl 2 NCO
XII. ACETYLENIC PESTICIDES
Cl Cl
Acetylenic compounds that have attained commercial sta- (B) A B
tus as pesticides are Barban (carbyne), Kerb (pronamide),
and Omite (propargite). The last-named compound is a
NHCO 2 CH 2 C C CH 2 Cl
miticide, while the other two are herbicides. Their uses
are outlined in Section VII.E. Their synthesis is summa-
Cl
rized as follows: Barban