Page 29 - 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 81

amine and is generally carried out at 30–50 atm and tem- salts or expensive transition metal catalysts. Reaction
peratures of 80–120 C. with alcohols in turn yields the corresponding methylketo
◦
open-chain carbonate in high yield (88–90%). Ethynyl-
CuCl
(CH 3 ) 2 C C CH CO 2 diolsresultingoodyieldthroughthesequentialconversion
N(C 2 H 5 ) 3
OH of the carbonate to the hydroxy ketone via water present
(CH 3 ) 2 C C CH 2
in the KOH, followed by ethynylation of the carbonyl pre-
O O cursor. The substitution of excess primary amine for the
C
tertiary amine cocatalyst results in good yields of disub-
O stituted methylene oxazolidones. The reactions are car-
◦
ried out at temperatures of 80–150 C at pressures below
MB(CO 2 )
40 atm.
◦
In the presence of excess, gaseous CO 2 at 80 C and
H 2 O
800 psig, methylbutynol reacts in 12 hr to form the cyclic MB(CO 2 ) −−−→ (CH 3 ) 2 C COCH 3 (85%)
carbonate MB(CO 2 ) in 90% yield. Liquid CO 2 has also −CO 2 | (9)
OH
been used successfully as both solvent and reactant be-
(a)
low its critical temperature (35 C) with secondary and
◦
tertiary acetylenic alcohols, 1-haloalkynols, and tertiary
acetylenic glycols. The mass action and solvent effect of CH 3
liquid CO 2 makes it possible for these reactions to proceed KOH−H 2 O C 2 H 2 |
MB(CO 2 ) −−−−→(a) −→ (CH 3 ) 2 C C C CH
readily at lower temperature and pressures, at faster reac- THF | |
tion rates, and with fewer by-products, particularly with OH OH (10)
secondary alkynols. However, the reaction is unsuccessful
with propargyl alcohol or secondary acetylenic glycols, MB(CO 2 ) + ROH −→ RO CO 2 C(CH 3 ) 2 CO CH 3
illustrating an unusual reaction specificity. The reaction (11)
of dimethyloctadiynediol (oxidative coupling product of
methylbutynol) and CO 2 leads to the formation of a bi-
functional carbonate with interesting potential in polymer MB(CO 2 ) + R NH 2 −→ (CH 3 ) 2 C C CH 2
chemistry. Acetylenic alcohols and diols reacted success-
ON R
◦
fullywithliquidCO 2 at20–30 Cunderpressure(500psig) ❙
are listed in Table X. Compounds (a), (b), (c), (e), and (f) C (12)
are tertiary alkynols or alkynediols, while (d) is a sec- O
ondary alkynol. The reaction gives highest yields with the
The cyclic carbonate from methylbutynol MB(CO 2 )
tertiary series.
can also be copolymerized with such monomers as methyl
The versatility of the cyclic carbonates is illustrated by
acrylate, styrene, and acrylonitrile. The acrylate copoly-
typical reactions carried out by Pasedach and co-workers.
mer was considerably harder than the homopolymer of
The alkynol (MB) is reacted in situ to form the cyclic
methyl acrylate and had a glass transition temperature of
carbonate MB(CO 2 ), which then undergoes further reac-
◦
◦
90 Cvs9 C for polymethylacrylate. By virtue of its car-
tion in the presence of an active hydrogen reactant.
bonate functionality, MB(CO 2 ) is an interesting reactive
Hydroxy ketones can be formed via reaction with wa-
monomer that not only provides increased hardness and
ter, followed by loss of CO 2 . This is an alternative method
strength to the polymer matrix, but can also be used to
of hydrating a triple bond without the use of mercury
make modified polymer structures by further reaction with
the reactive ring system.
TABLE X Acetylenic Compounds Reacted with
Liquid Carbon Dioxide
B. Arylacetylenes from Methylbutynol
Yield of cyclic
Acetylenic compound carbonate (%) and Aromatic Compounds
Selwitz and co-workers at Gulf Research and Devel-
(a) 3-Methyl-1-butyn-3-ol 90
opment Company have disclosed interesting technol-
(b) 1-Chloro-3-methyl-1-butyn-3-ol 76
ogy for the production of substituted arylacetylenes,
(c) 1-Ethynylcyclohexanol 87
where the ethynyl group is directly attached to the aro-
(d) 4-Methyl-1-pentyn-3-ol 66
matic nucleus. Arylacetylenes are normally quite diffi-
(e) 2,5-Dimethyl-3-hexyne-2,5-diol 93
cult to prepare by direct substitution. The important fea-
(f) 2,7-Dimethylocta-3,5-diyne-2,7-diol 76
tures of this process are the reaction of an active aryl