Page 17 - Academic Press Encyclopedia of Physical Science and Technology 3rd Organic Chemistry

P1: GLQ Revised Pages
Encyclopedia of Physical Science and Technology EN001F-4 May 7, 2001 16:19

Acetylene 69

FIGURE 4 Butynediol–propargyl alcohol process. (1) Acetylene storage; (2) compressor; (3) recycle compressor;
(4) pressure reactor; (5) vent; (6) separator; (7) pumps; (8) stripping still; (8a) recycle formaldehyde; (9) formaldehyde
storage; (10) NaOH feed; (11) settling tank; (12) waste effluent; (13) butynediol storage; (14) recycle C 2 H 2 stream
for vinylpyrrolidone production. [Reprinted from Tedeschi, R. J. (1982). “Acetylene-Based Chemicals from Coal and
Other Natural Resources,” p. 105, courtesy of Dekker, New York.]

at 90–130 C. The products resulting from this reaction, in commercial practice. Below is shown the formation of
◦
butynediol and propargyl alcohol, are formed in approxi- sodium acetylide in liquid ammonia and its reaction with
mately 9:1 ratio, with butynediol the predominant product. a vitamin E intermediate, geranylacetone (GA), to yield
The reaction proceeds readily (exothermic) in total con- the important terpene alkynol, dehydronerolidol (DHN):
versions and selectivity of well over 90%.
Fe(NO 3 ) 3 1
CuC 2 H 1. Na + Liquid NH −−−→ NaNH 2 + H 2 (3)
3
HCHO + C 2 H 2 −−−→ H C C CH 2 OH −33 C 2
◦
Propargyl alcohol
NH 3
2. NaNH 2 + C 2 H 2 −→ NaC 2 H + NH 3
+ HO CH 2 C C CH 2 OH
Butynediol
CH 3
Higher aldehydes or reactive methyl ketones fail to re- |
act in the Reppe system. Even a reactive aldehyde such 3. (CH 3 ) 2 C CH (CH 2 ) 2 C CH (CH 2 ) 2
GA
as acetaldehyde reacts very slowly and gives only an 18%
COCH 3 + C 2 H(NH 3 )
◦
conversion in 22 hr at 125 C. In contrast, formaldehyde

reacts exothermically and is the basis for the continuous  1.NaC 2 H
2.H 2 O−NH 4 Cl
operation in current Reppe plants. Flow diagrams of the (4)
butynediol–propargyl alcohol process and the continuous
process for the production of all Reppe products are shown CH 3 CH 3
| |
in Figs. 4 and 5, respectively. The commercial importance (CH 3 ) C CH (CH 2 ) C CH (CH 2 ) C C CH
2 2 2
of these acetylene-based products and their estimated pro- |
OH
duction volumes are discussed in Sections VI.A–VI.D.
DHN
(5)
C. Sodium and Lithium Acetylides
This technology is used by Hoffmann–La Roche to pre-
in Liquid Ammonia
pare intermediates for the manufacture of vitamins A and
Although alkali metal acetylides can be prepared in polar E. The process has been in operation since the early 1950s.
organic solvents by the reaction of acetylene with alkali The use of lithium acetylide is preferred for more sensitive
metal dispersions, the preparation and synthetic use of or less reactive carbonyl compounds. Reactions (3)–(5)
either sodium or lithium acetylides in liquid ammonia has are run consecutively in liquid ammonia without isola-
proved to be the preferred route both in the laboratory and tion. The formation of the alkali metal acetylide (sodium,