Note: Descriptions are shown in the official language in which they were submitted.
8C~-2157
~073468
This invention relates to a process for producing diols from their
carboxylate esters, with the simultaneous production of N,N-dialkyl
carboxylic acid amides. More particularly, this invention relates to a
~process for simultaneously producing aliphatic diols and N,N-dimethylacet-
amide or N,N-dimethylformamide from the corresponding diol mono- and di-
carboxylate esters.
BACKGROUND OF THE INVENTION
The aliphatic diols constitute a class of valuable compounds. They
have wide utility in manufacture of polyesters and polyurethanes, and as
solvents and synthetic intermediates. There are a nu~ber of methods known
in the art by which diol carboxylate acid esters may be converted to these
more useful diols. Aqueous base hydrolysis is unacceptable in that it ~ -
involves the formation of salts which must be treated for recovery of their
valuable components. With esters of 1,4-butanediol especially, acidic
conditions can be employed only with severe restrictions, so as to avoid
the cycliæation reaction producing tetrahydrofuran.
In Canadian applications of Will Dockery Merritt, Jr.~Serial
No. 196,825 dated April 4, 1974, and John E. Corn et al, Ser.
No. 209,309, dated Sept/16/1974, both assigned to the same
assignee as this invention, processes involving alcoholysis of
diol esters promoted by alkali metal hydroxide and acidic ion -
exchange resins, respectively, are disclosed. In a Canadian
application of William Edward Smith, Ser. No. 217,507 dated
Jan/7/1975 and assigned to the same assignee as this invention
the vapor phase alcoholysis of diol esters over magnesia
catalysts is described.
The N,N-dialkyl carboxylic acid amides are also valuable compounds,
N,N-dimethylacetamide and N,N-dimethylformamide in particular have found
wide utility in spinning of fibers and in other solvent applications. The
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1073468
method by which most N,N-dimethylacetamide is manufactured involves the re-
action of dimethylamine and acetic acid under conditions of elevated tempera-
ture and pressure as shown in U.S. Patents 2,667,511 and 3,006,956. Acetic
anhydride may also be employed as the acylating agent as disclosed in U.S.
Patent 3,006,956. In more recently described methods, N,N-dimethylacetamide
is prepared from trimethylamine and carbon monoxide in the presence of a
cobalt carbonyl catalyst as described in U.S. Patent 3,407,231, or by
reaction of dimethylamine and ketene as disclosed in U.S.S.R. Patent
183,731.
N,N-dimethylacetamide has been formed in relatively low yield by
reaction of dimethylamine and polyvinyl acetate in methanol solvent in
absence of added catalyst as shown in U.S. Patent 3,197,450. It has also
been produced by reaction of aqueous dimethylamine with allyl acetate or
vinyl acetate in the presence of a basic ion exchange resin catalyst as
described in Netherlands Application 6,601,128.
DESCRIPTION OF THE INVENTION
It has been discovered that diols can be obtained by a highly
efficient method which involves reaction of their acetate esters with
dimethylamine. N,N-dimethyl carboxylic acid amides are produced simultan-
eously. The process is illustrated for the case of conversion of 4-
acetoxybutanol to 1,4-butanediol and N,N-dimethylacetamide in equation (1):
(1) 0 0
ll "
2 4 3 ( 3)2 ~ HO(CH2)4 OH + ~CH3)2 N C CH3
An important feature of this invention relates to the use of a diol
as a solvent and reaction medium for an ester aminolysis process in which
more of it is to be produced. For example, ethylene glycol can be employed
to significant advantage as solvent for the conversion of ethylene glycol
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~073468
diacetate and dimethylamine to ethylene glycol and N,N-dimethylacetamide.
The catalysts useful for this transformation (such as sodium methoxide)
dissolve readily in this environment and the medium is made substantially
more polar. For these reasons, the reaction rate is greatly accelerated.
The amide and stoichiometric amount of diol can be readily isolated by
distillation; the residual diol and catalyst can be recycled for use with
another charge of diol ester and dimethylamine.
me process may be employed for conversion of a wide variety of
diol carboxylic acid esters including aliphatic, cycloaliphatic and aromatic
diol esters. Preferrably~ these are aliphatic diol esters. Most preferred
diol esters include acetates and formates of 1,4-butanediol, 2-methyl-1,3- ~-
propanediol, 1,2-butanediol, 1,3-propanediol, 1,2-propanediol, ethylene gly-
col, 1,6-hexanediol, 1,5-pentanediol, 2-methyl-1,4-butanediol and 1,4-di- -
(hydroxymethyl) cyclohexane. The method is particularly applicable to
15 production of a mixture of 1,4-butanediol, 2-methyl-1,3-propanediol and
1,2-butanediol from a mixture of the corresponding acetate esters.
The dialkyl amines included within the scope of this invention are !
those wherein each alkyl group contains from 1 to 4 carbon atoms.
As disclosed suPra, a diol of the kind to be produced in the aminol-
ysis may be employed as the solvent to substantial advantage. The relativeamount used is not critical. One to three equivalents of the diol constitute
convenient amounts of the diol solvent that greatly facilitate the process.
The presence of added diol is not required for the aminolysis to proceed,
however, especially in cases where the diol ester starting material is wholly
or partly composed of the mono-ester derivative. (The term "diol esters"
is meant to include both the mono- and di-ester derivatives of diols. The
term may also refer to mixtures of diol esters as well as to particular
diol esters.)
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8CH-2157
The catalysts that may be used within the scope of this invention
are bases that are known in the art to promote aminolysis and~or transesteri-
fication reactions. These include alkali metal and alkaline earth metal
hydroxides, alkoxides and carboxylates, examples of which are sodium hydr-
oxide, potassium hydroxide, magnesium hydroxide, sodium methoxide and
lithium acetate. Strongly basic ion exchange resins may also be employed
as catalyst; resins bearing the quaternary ammonium hydroxide function
are very effective.
The process can be effected in the absence of added catalyst,
however, particularly when full solvent quantities of the diol are present
and the conditions are more rigorous. Even in these cases, the reactions
are much slower, so it is to substantial practical advantage to employ a
catalyst.
The temperature at which the process can be carried out varies
widely and is not critical. Temperatures from room temperature to about
250DC are found suitable. A preferred temperature range is from about 60C
to about 180C.
A wide range of pressures may be used within the scope of this -
invention since pressure is not critical. Preferred pressure ranges are
those that are required to contain the dialkyl amine at the operating
temperature.
The process can be efficiently carried out by heating the combined
diol ester, amine, free diol and catalyst in an autoclave until a satisfac-
tory extent of de-esterification and amide formation is obtained. The
excess amine can then be vented and recovered for recycle. The amide and
diol products can be isolated by distillation, with the catalyst and an
amount of the diol suitable for use with the next charge of diol ester and
amine left as the residue. Thus in operation the net transformation involves
only stoichiometric quantities of the diol ester and amine.
8CH-2157
PREFERRED EMBODIMENT OF THE INVENTION
The following examples are set forth to illustrate ~ore clearly
the principle and practice of this invention to those skilled in the art.
Vnless otherwise specified, where parts or percents are mentioned, they
are parts or percents by weight.
EXAMPLE I `
A mixture of 9.8 grams of 1,4-butanediol diacetate, 8.4 grams of
dimethylamine, 9.0 grams of 1,4-butanediol and 0.2 grams of sodium
methoxide was heated in a six inch by one inch diameter Teflon~gasketed
glass pressure vessel at 120-135C for one hour. The product mixture was
then cooled and subjected to quantitative gas-liquid partition chromatography
(glpc) analysis. The presence of 9.6 grams of N,N-dimethylacetamide (98%
yield) and 13.9 grams of 1,4-butanediol (an increase of 4.9 grams, which
corresponds to 96% yield) was indicated. The only other product detected
was a trace of methanol derived from the catalyst by alkoxide exchange. ;
EXAMPLE II
A mixture of 9.8 grams of 1,4-butanediol diacetate, 8.4 grams of
dimethylamine, 9.0 grams of 1,4-butanediol and 0.2 grams of sodium -`
methoxide was stirred in a closed vessel without external heating. The
progress of the reaction was monitored by glpc analysis. After one hour,
about 90% of the diacetate had been converted; after two hours, none could
be detected (some 4-acetoxybutanol was still present). After 24 hours, - -~
the reaction was complete--the only products detected were 13.8 grams of
1,4-butanediol (an increase of 4.8 grams, which corresponds to 95%
yield) and 9.5 grams of N,N-dimethylacetamide (97% yield).
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EXAMPLE III
A mixture of 8.7 grams of 1,4-butanediol diacetate, 9.0 grams of
dimethylamine, 17.3 grams of 1,4-butanediol and 0.2 grams of sodium
methoxide was heated at 175C in a pressure bottle for 30 minutes.
Quantitative glpc analysis of the cooled product mixture showed the presence
of 8.6 grams of N,N-dimethylacetamide (99% yield). There was a corresponding
increase in the amount of 1,4-butanediol.
EXAMPLE IV
A mixture of 11.1 grams of ethylene glycol diacetate, 10.9 grams
of dimethylamine, 10.0 grams of ethylene glycol and 0.3 grams of sodium
methoxide was heated at 180C and autogenous pressure for one hour as in
Example I. Quantitative glpc analysis of the cooled product mixture revealed
the presence of 12.8 grams of N,N-dimethylacetamide (97% yield) and 14.6
grams of ethylene glycol (an increase of 4.6 grams, which corresponds to
98~ yield). No other products were detected.
EXAMPLE V
This example is included to demonstrate the relative inefficiency
of the aminolysis when the diol solvent modification is not employed. ,
A mixture of 7.6 grams of ethylene glycol diacetate, 7.4 grams of
dimethylamine and 0.3 grams of sodium methoxide was heated at 180C and
autogenous pressure as in Example IV. A solid phase remained present
throughout the heating period (six hours), and the mixture gradually
darkened. On cooling and glpc analysis, it was found that little (less
than 15%) conversion to N,N-dimethylacetamide had occurred.
EXAMPLE VI
A mixture of 10.0 grams of dimethylamine, 13.2 grams of crude butane-
diol monoacetate derived from allyl acetate via the oxo process (containing,
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107346~3
as determined by glpc analysis of a completely acetylated sample, derivatives
of 1,4-butanediol, 2-methyl-1,3-propanediol and 1,2-butanediol in 15.4:1:2.5
proportions), and 0.3 grams of sodium methoxide was heated in a pressure
vessel at 120C for three hours. According to glpc analysis, the product
mixture contained essentially only the diols and N,N-dimethylacetamide
(5.6 grams, corresponding to 64% yield based on "butanediol monoacetate".)
EXAMPLE VII
A mixture of 16.7 grams of the crude butanediol monoacetate
described in Example VI, 12.7 grams of dimethylamine, 9.0 grams of butane-
diol and 0.3 grams of sodium methoxide was heated in a pressure vessel at
120C for two hours. Analysis of the product mixture showed that complete -
conversion to the diols had been effected, and that 8.4 grams of N,N-
dimethylacetamide had been produced (75% yield based on "butanediol mono-
acetate").
EXAMPLE VIII
Dimethylamine was bubbled into a mixture of 5.6 grams of ethylene -
glycol diacetate, 6.2 grams of ethylene glycol and 0.3 grams of sodium `~
methoxide in a vessel fitted with a dry ice condenser. An exothermic reaction
resulted--the reaction reached 80C spontaneously. Analysis of the mixture
after 30 minutes showed that complete conversion of the di-ester to ethylene ~-
glycol and N,N-dimethylacetamide had been effected.
The product mixture was distilled under reduced pressure until the -
amide and an approximately stoichiometric amount of ethylene glycol were
removed. The residue was combined with another portion of ethylene glycol
diacetate and more dimethylamine, whereupon the exothermic reaction again
occurred. The catalyst seemed to have lost none of its activity.
~ ~~~ 8CH -2157
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. 1073468
EXAMPLE IX
A mixture of 11.8 grams of ethylene glycol diformate, 13.0 grams
of dimethylamine, 6.2 grams of ethylene glycol and 5.0 grams of Rexy ~ 201
basic ion exchange resin (R4N OH form) was stirred at 25C for 30 minutes.
Analysis of the supernatant liquid showed that complete conversion to
ethylene glycol and N,N-dimethylformamide had been effected in that time.
A quantitative glpc analysis showed the presence of 13.7 grams of N,N-
dimethylformamide (94% yield) and 11.6 grams of ethylene glycol (an increase
of 5.4 grams, which corresponds to 87% yield).
EXAMPLE X
A mixture of 11.8 grams of ethylene glycol diformate and 6.2 grams
of ethylene was heated to 80C and treated with gaseous dimethylamine in
absence of added catalyst. The solution was maintained at 80-120C while
the amine was bubbled in over a three hour period. Analysis of the mixture
after this treatment showed that an essentially complete de-esterification ~ ~ -
had been effected and that 12.6 grams of N,N-dimethylformamide had been
produced (86~ yield).
It will thus be seen that the objects set forth above among those
made apparent from the preceding description are efficiently attained and
- 20 since certain changes may be made in carrying out the above process and --
in the composition set forth without departing from the scope of this
invention, it is intended that all matters contained in the above descrip-
tion shall be interpreted as illustrative and not in a limiting sense.
