N, N-Dimethylacetamide

N , N- Dimethylacetamide ^[1] ^[2]
N , N- Dimethylacetamide
Are common
Abbreviations	DMAA
Traditional names	Acetic Acid Dimethylamide
Chem. formula	C 4 H 9 NO
Rat formula	CH 3 CON (CH 3 ) 2
Physical properties
condition	colorless liquid
Molar mass	87.12 g / mol
Density	0.9366 g / cm³
Ionization energy
Thermal properties
T. melt.	–20 ° C
T. bale.	165.5 ° C
T. aux.	70 ° C
T. svpl.	490 ° C
Etc. blast	2-11.5%
Cr. pace.	364 ° C
Cr. pressure	38.7 atm
Like heat resistant.	175.6 J / (mol · K)
Enthalpy of Education	–278.3 kJ / mol
Enthalpy of melting	10.42 kJ / mol
Enthalpy of boiling	43.4 kJ / mol
Sublimation Enthalpy	50.2 kJ / mol
Steam pressure
Chemical properties
pK a	0.19
Dielectric penetration.	37.78
Optical properties
Refractive index	1,4376
Structure
Dipole moment	3.80 D
Classification
Reg. CAS number	127-19-5
PubChem
Reg. EINECS number
Smiles
Inchi
Reg. EC number	204-826-4
RTECS	AB7700000
Chebi
ChemSpider
Security
MPC	1 mg / m³
LD 50	4.2 g / kg (mice, oral)
H phrases	H312 + H332 , H319 , H360
P-phrases	P201 , P280 , P305 + P351 + P338 , P308 + P313
Signal word	Dangerously
GHS icons
NFPA 704	2 2 0

N , N- Dimethylacetamide - an organic substance, acetic acid dimethylamide.

Physical Properties

It is a colorless hygroscopic liquid. Dimethylacetamide mixes with water and organic solvents, dissolves well unsaturated aliphatic hydrocarbons and many inorganic compounds. With acetic acid, dimethylacetamide forms an azeotropic mixture (21.1% by weight of acetic acid, mp. 170.8 ° C) ^[4] .

Chemical Properties

Dimethylacetamide is a very weak base, while the basicity increases in a solution of acetic anhydride , in which it can be titrated with a 0.1 M solution of perchloric acid in acetic acid ^[4] .

Dimethylacetamide undergoes hydrolysis in an acidic and alkaline environment, enters into the reaction of alcoholysis and reacylation ^[4] .

{\mathsf {CH_{3}CON(CH_{3})_{2}+ROH{\xrightarrow {H^{+}}}CH_{3}COOR+(CH_{3})_{2}NH}}

{\ displaystyle {\ mathsf {CH_ {3} CON (CH_ {3}) _ {2} + ROH {\ xrightarrow {H ^ {+}}} CH_ {3} COOR + (CH_ {3}) _ {2} NH}}}

{\mathsf {CH_{3}CON(CH_{3})_{2}+RCOOH\rightarrow RCON(CH_{3})_{2}+CH_{3}COOH}}

{\ displaystyle {\ mathsf {CH_ {3} CON (CH_ {3}) _ {2} + RCOOH \ rightarrow RCON (CH_ {3}) _ {2} + CH_ {3} COOH}}}

Getting

Industrial production of dimethylacetamide.

In industry, dimethylacetamide is obtained by the interaction of dimethylamine :

with acetic acid

{\mathsf {CH_{3}COOH+(CH_{3})_{2}NH{\xrightarrow {40^{o}C}}CH_{3}COOH*HN(CH_{3})_{2}}}

{\ displaystyle {\ mathsf {CH_ {3} COOH + (CH_ {3}) _ {2} NH {\ xrightarrow {40 ^ {o} C}} CH_ {3} COOH * HN (CH_ {3}) _ { 2}}}}

{\mathsf {CH_{3}COOH*HN(CH_{3})_{2}{\xrightarrow {135-140^{o}C}}CH_{3}CON(CH_{3})_{2}+H_{2}O}}

{\ displaystyle {\ mathsf {CH_ {3} COOH * HN (CH_ {3}) _ {2} {\ xrightarrow {135-140 ^ {o} C}} CH_ {3} CON (CH_ {3}) _ {2} + H_ {2} O}}}

In the first process, in the first stage, dimethylamine acetate is obtained at 40 ° C, which is then dehydrated in a stream of dimethylamine at 135-140 ° C.

with acetic anhydride :

{\mathsf {(CH_{3}CO)_{2}O+(CH_{3})_{2}NH{\xrightarrow {t}}CH_{3}CON(CH_{3})_{2}+CH_{3}COOH}}

{\ displaystyle {\ mathsf {(CH_ {3} CO) _ {2} O + (CH_ {3}) _ {2} NH {\ xrightarrow {t}} CH_ {3} CON (CH_ {3}) _ { 2} + CH_ {3} COOH}}}

with esters of acetic acid:

{\mathsf {CH_{3}COOR+(CH_{3})_{2}NH{\xrightarrow {t}}CH_{3}CON(CH_{3})_{2}+ROH}}

{\ displaystyle {\ mathsf {CH_ {3} COOR + (CH_ {3}) _ {2} NH {\ xrightarrow {t}} CH_ {3} CON (CH_ {3}) _ {2} + ROH}}}

There is also a vapor-phase synthesis method in which water-taking catalysts are used ( aluminum oxide , etc.). The conversion of acetic acid in one pass in this synthesis is 95–99% ^[4] .

Laboratory methods for the preparation of dimethylacetamide.

Preparative syntheses are based on the reaction of dimethylamine with acetic anhydride, acetyl chloride or ketene .

{\mathsf {CH_{3}COCl+(CH_{3})_{2}NH{\xrightarrow {AlCl_{3}}}CH_{3}CON(CH_{3})_{2}+HCl}}

{\ displaystyle {\ mathsf {CH_ {3} COCl + (CH_ {3}) _ {2} NH {\ xrightarrow {AlCl_ {3}}} CH_ {3} CON (CH_ {3}) _ {2} + HCl }}}

{\mathsf {H_{2}C=C=O+(CH_{3})_{2}NH\rightarrow CH_{3}CON(CH_{3})_{2}}}

{\ displaystyle {\ mathsf {H_ {2} C = C = O + (CH_ {3}) _ {2} NH \ rightarrow CH_ {3} CON (CH_ {3}) _ {2}}}}

The interaction of methanol with acetonitrile leads to the formation of dimethylacetamide:

{\mathsf {2CH_{3}OH+CH_{3}CN{\xrightarrow {CuCN}}CH_{3}CON(CH_{3})_{2}+H_{2}O}}

{\ displaystyle {\ mathsf {2CH_ {3} OH + CH_ {3} CN {\ xrightarrow {CuCN}} CH_ {3} CON (CH_ {3}) _ {2} + H_ {2} O}}}

Carbonylation of trimethylamine is also a method for producing dimethylacetamide:

{\mathsf {(CH_{3})_{3}N+CO\rightarrow CH_{3}CON(CH_{3})_{2}}}

{\ displaystyle {\ mathsf {(CH_ {3}) _ {3} N + CO \ rightarrow CH_ {3} CON (CH_ {3}) _ {2}}}}

Reacylation reactions of dimethylformamide or hexametapol are also used ^[4] :

{\mathsf {HCON(CH_{3})_{2}+CH_{3}Cl{\xrightarrow {AlCl_{3}}}CH_{3}CON(CH_{3})_{2}+HCl}}

{\ displaystyle {\ mathsf {HCON (CH_ {3}) _ {2} + CH_ {3} Cl {\ xrightarrow {AlCl_ {3}}} CH_ {3} CON (CH_ {3}) _ {2} + HCl}}}

{\mathsf {[(CH_{3})_{2}N]_{3}PO+CH_{3}COCl{\xrightarrow {AlCl_{3}}}CH_{3}CON(CH_{3})_{2}+[(CH_{3})_{2}N]_{2}POCl}}

{\ displaystyle {\ mathsf {[(CH_ {3}) _ {2} N] _ {3} PO + CH_ {3} COCl {\ xrightarrow {AlCl_ {3}}} CH_ {3} CON (CH_ {3 }) _ {2} + [(CH_ {3}) _ {2} N] _ {2} POCl}}}

.

Dimethylacetamide can be prepared by reacting dimethylamine with methyl acetate at elevated temperature and pressure in the presence of sodium methylate .

{\mathsf {CH_{3}COOCH_{3}+(CH_{3})_{2}NH{\xrightarrow {CH_{3}ONa}}CH_{3}CON(CH_{3})_{2}+CH_{3}OH}}

{\ displaystyle {\ mathsf {CH_ {3} COOCH_ {3} + (CH_ {3}) _ {2} NH {\ xrightarrow {CH_ {3} ONa}} CH_ {3} CON (CH_ {3}) _ {2} + CH_ {3} OH}}}

To purify dimethylacetamide, it is mixed with barium oxide for several days, then boiled over barium oxide for 1 hour, distilled under reduced pressure, and stored over molecular sieves ^[5] .

Application

Dimethylacetamide is used in the production of synthetic fibers and films, for the separation of dienes and styrene from the pyrolysis products of oil fractions. It is also used as a catalyst or reaction medium in halogenation , alkylation, and cyclization reactions ^[4] .

Toxicity

N, N-Dimethylacetamide is slightly toxic LD ₅₀ = 4.2 g / kg (mouse, oral). With prolonged contact with the skin causes intoxication of the body. MPC for the working area is 1 mg / m ³ ^[6] .

Notes

↑ Dean JA Lange's Handbook of Chemistry. - 15th Ed. - McGraw-Hill, Inc, 1999. - ISBN 0-07-016384-7 .
↑ Sigma-Aldrich. N , N- Dimethylacetamide (neopr.) . Date of treatment November 9, 2013.
↑ ¹ ² http://www.cdc.gov/niosh/npg/npgd0218.html
↑ ¹ ² ³ ⁴ ⁵ ⁶ Chemical Encyclopedia. In five volumes. / Ch. ed. I.L. Knunyants. - M .: Soviet Encyclopedia, 1990. - T. 2. - P. 62.
↑ Armarego WLF, Chai CLL Purification of Laboratory Chemicals. - 6th Ed. - Elsevier, 2009 .-- S. 129. - ISBN 978-1-85617-567-8 .
↑ Harmful substances in industry. Handbook for chemists, engineers and doctors. Ed. 7th, per. and add. In three volumes. Volume I. Organic matter. Ed. merit activist science prof. N.V. Lazareva and Dr. honey. Sciences E.N. Levina. L., “Chemistry,” 1976. 592 pp., 27 tablets, bibliography — 1850 titles.

Links

Sigma-Aldrich. IR spectrum of dimethylacetamide (neopr.) . Date of treatment November 10, 2013.
Sigma-Aldrich. NMR spectrum of dimethylacetamide (neopr.) . Date of treatment November 10, 2013.

[1] Dean JA Lange's Handbook of Chemistry. - 15th Ed. - McGraw-Hill, Inc, 1999. - ISBN 0-07-016384-7 .

[2] Sigma-Aldrich. N , N- Dimethylacetamide (neopr.) . Date of treatment November 9, 2013.

[_20b826da82f9dfba-3] ¹ ² http://www.cdc.gov/niosh/npg/npgd0218.html

[ХЭ-4] ¹ ² ³ ⁴ ⁵ ⁶ Chemical Encyclopedia. In five volumes. / Ch. ed. I.L. Knunyants. - M .: Soviet Encyclopedia, 1990. - T. 2. - P. 62.

[Armarego-5] Armarego WLF, Chai CLL Purification of Laboratory Chemicals. - 6th Ed. - Elsevier, 2009 .-- S. 129. - ISBN 978-1-85617-567-8 .

[A-6] Harmful substances in industry. Handbook for chemists, engineers and doctors. Ed. 7th, per. and add. In three volumes. Volume I. Organic matter. Ed. merit activist science prof. N.V. Lazareva and Dr. honey. Sciences E.N. Levina. L., “Chemistry,” 1976. 592 pp., 27 tablets, bibliography — 1850 titles.