THE NITROPARAFFINS NEW SYNTHETICS FOR SYNTHESIS C. L. GABRIEL Commercial Solvents Corporation, New York, N. Y.
from aniline. The nitration of coal tar hydrocarbons, especially benzene, became the first important step in the preparation of numerous derivatives.
The large-scale production of the nitroparaffins and some of their derivatives represents a new chapter in the development of the synthetic organic chemical industry. Rlany reactions for these products are indicated, but they represent only a small portion of the possible total. It is therefore evident that these new chemicals can form the basis for industrial research for years to come, and that the products will help to expand greatly the scope of chemical manufacture and utility.
T
HE synthetic organic chemical industry was born about the middle of the nineteenth century when, within a few years of each other, nitrocellulose and nitroglycerin were discovered, and the first aniline dyestuff was prepared in the laboratory. Nitric acid is an essential raw material for making each of these products. When considering the development of synthetic organic chemistry, nitrocellulose and nitroglycerin may be eliminated and emphasis placed on the production of thousands of dyestuffs, rubber chemicals, and pharmaceuticals, many of which are made
887
INDUSTRIAL AND ENGINEERING CHEMISTRY
888
VOL. 32, NO. 7
FIGURE 1. NITROMETHANE TREE CHaNO2
I
i ~
I
I
1 1
*!ids
1
Z,?.,ERS
I
I
1
Acids
V
I.
CHClsiTOz V CClaKOz-
Acid
4
CHaNHn
I
1
[
NOH
I LCH=N
I
I Reduhion
V
/ H g Cl;
CeH,CHOfI-COOH
V
C H I O H - C H ~ N H ~ (CH2OH)zCHXHs ( C H s 0 H ) C N H s
\I/
I
CHiNOn /
'Y,STERS
Redlction
V
Acids
I
~
I
Reduotion
1
I
(C=KO)zHg
Higher F a t t y ,Acids
J.
KeTnes
OXIMES
I
Reduction
Alkali hits
I
oi S i t r o iraffins
SOAPS O F A M I N O H Y D R O X Y COMPOUNDS
Aldehydrand
DINITROP RAFFINS
4
Heat
AMIDES
In this country large-scale organic chemical production did not begin to assume any importance until the first World War was well under way, and our textile and pharmaceutical manufacturers could no longer procure the necessary products which had come from Europe. By the time the war ended, a substantial industry using chiefly coal tar hydrocarbons as raw materials had been built up. At about the same time important manufacturing operations began to be developed in the United States for the production of aliphatic chemicals. Included in these products should be mentioned methyl, ethyl, propyl, butyl, and amyl alcohols, acetone, methyl ethyl ketone, ethylene glycol, and their many derivatives. Now a new synthetic organic development is being launched. Kitric acid, which played so important a part in the growth of the coal tar chemical industry, is reacted not with benzene, toluene, or phenol, but with an aliphatic hydrocarbon to produce nitroparaffins. The first commercial units for the production of these materials have just begun t o operate a t Peoria, Ill.
Production Nitromethane, nitroethane, 1-nitropropane, and Znitropropane are being made in the new plant. At a later date nitroparaffins with longer carbon chains will be available. These four lowest members of the nitroparaffin series are formed simultaneously when propane and nitric acid or nitrogen oxides are brought together in a vapor state at elevated temperatures. The nitroparaffins are separated as a crude mixture from the unconverted hydrocarbons and nitrogen oxides, which are recycled through the reaction chamber. The individual nitro compounds are obtained by distillation and chemical purification. I n its simplest form a nitroparaffin plant may be conceived t o consist of a reaction chamber, equipment for separating the nitroparaffin mixture from the unconverted raw materials, and purification apparatus for the final products. Actually the production units must be much more complicated, since side reactions form both gaseous and liquid impurities which must be removed. The photographs indicate the complexity of some of the equipment, although they cannot show the special materials of construction required to withstand corrosive action a t elevated temperatures.
TABLEI. PHYSICAL CONSTANTS OF NITROPARAFFINS Nitromethane Formula CHsNOz Mol. weight 61 Boiling point, C. 101 Freezing point, ' C. 29 Flash Doint (Tagliabue open cup) ' F. 95 Index of refraition, 200 c. 1.3817 Specific gravity. 20/ 2Q" c. 1.139 Weight per U. 8.gal., Ib. 9.5 Water-white Color Mild Odor Soly. in 100 cc. water, cc. 9.10 Soly. of water in 100 cc. nitroparaffin, cc. 2.2 Va or p r m u r e a t 20' mm. Hg 27.8 6.12 PH d.01M aq. soln. p H water satd. with 4.01 nitroparaffin p H nitroparaffin satd. with water 4.82 Surface tension a t 20° C., dynes/cm. 37 Evaporation rate 4 (I-butanol)
-
8.
Nitroethane I-Nitropropane C H I C H ~ N O ~CHaCHd2HzNOt 89 75 114 132 90 108
-
-
2-Nitropropane CHrCHNOiCHa 89 120 -93
82
93
75
1.3917
1.4015
1.3941
1.052
1.003
0.992
8.8 Water-white Mild
8.4 Water-white Mild
8.3 Water-white Mild
4.5
1.4
1.7
0.9
0.5
0.6
15.6 5.20
7.6 5.61
12.9 5.33
3.85
4.33
4.29
3.75
4.06
3.00
31
30
....
3
2
2.5
Utilization Since the n i t r o p a r f i s have never before been made in quantity, the question of their utilization naturally arises. An extended study of markets has shown that a substantial proportion of the initial production capacity can be sold. The sales survey included the nitroparaffins and a number of derivatives. The physical constants of those which are being produced are given in Tables I and 11. From the utilization angle the nitroparaffins may again be compared to nitrobenzene since it appears that a large proportion will be used as raw materials for chemical synthesis. This situation may change considerably when the nitroparaffins can be offered a t lower prices so that they can better compete with solvents which are today being used to dissolve nitrocellulose and various resins. However, they do possess specific advantages when used as solvents for cellulose
JULY, 1940
INDUSTRIAL AND ENGINEERING CHEMISTRY
889
FIGGRE 2. NITROETHANE TREE^ CHaCHzSOz ~
PLCHO
i\ J.
CHzOH C I H ~ C H O H - C H S O ~ - C H ~ CoHaCHOH-CtIYOGHa -4Hs-CKOz
i
1
I
\
-CHaCHCINO2
CHaOH
CHsCCLNO2
Reduction 1
Has04 I -t H10
S t H
CHaCHzSH2 CH&H=N7
1
CHaCOOH
+
NH2O,H.H*SOd CHsCHO
AMINES AHzOH
soa'ps I
a I-Nitropropane euterv into the same reactions as nitroethane except t h a t the products formed contain a n additional CHI. group.
Heat V
acetate and Vinylites. In this article emphasis will be placed on the chemical reactions and the chemical utilization of the nitroparaffins, as the limits of this field are still to be found. Hundreds of organic chemicals already have been synthe-
sized from the nitroparaffins, and there is every indication that this number can be expanded many times. The nitroparaffin "trees", shown in Figures 1,2, and 3, will undoubtedly bear many additional branches in the near future.
Chemical Properties The nitroparaffins were discovered by Victor Meyer in 1872. By reacting ethyl iodide with silver nitrite, he obtained a mixture of isomers, ethyl nitrite, and nitroethane. Nitroparaffins are somewhat acidic in the presence of water, owing t o the formation of nitronic acids. Although the normal structure of a primary nitroparaffin is 0
t
RC:H*--N=O
in the presence of water this changes to 0
t
RCH=N-OH
The nitronic acids will not dissolve in a sodium carbonate solution but are neutralized by a strong base. A sodium hydroxide solution will form a sodium salt by replacing the hydrogen in the hydroxyl group with sodium. Since the nitroparaffins are weak acids, they can be regenerated from the sodium salt by carbon dioxide. The corresponding amines are formed with excellent yields when nitroparaffins are treated with hydrogen or other reducing agents: CH&'OS
COMPLEXPIPISGSYSTEU USEDISNITROP~ R I F F I XhI IXEF~CTURE
(CH,),CHX02
Hz
+ CHSNH9 Hz &
(CHB)lCHSH*
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INDUSTRIAL AND ENGINEERING CHEMISTRY
VOL. 32, NO. 7
nitrous acid, the solution is colorless in the presence of an alkali. Strong mineral acids in the presence of water convert the primary nitroparaffins into a hydroxylammonium salt of the mineral acid and a fatty acid having the same number of carbon atoms as the nitroparaffins. It is believed that hydroxamic acid is first formed : HzSOa NOH HzO CH~CHZCHZNOZ CHsCHzCJ ---f \OH CH3CHZCOOH NH2OH.HpSOd
+
When alkali salts of the nitroparaffins are added to strong sulfuric acid, the primary products form aldehydes and the secondary yield ketones: &SO4 CHsCHNOzNa -+ CH,CHO (CHJ2CNO&a
HzSOc
+ (CH&CO
Although dilute alkali converts the nitroparaffins to their salts, strong potassium hydroxide reacts with nitromethane to form the potassium salt of methazonic acid:
Hydrolysis of methazonic acid yields nitroacetic acid, which on reduction is converted into aminoacetic acid (glycine) :
SEPARATION AND PURIFICATION
TOWER O F THE
NITROPARAFFIN PLANT
Nitrohydroxy Compounds Meyer showed that by gradual reduction an alkyl hydroxylamine is formed as an intermediate product ( 3 ): Hz CHsNOz + CH3NHOH Reduction of the nitroparaffins with stannous chloride yields oximes: -. SnG12 I
CHsCHzN02
+
CH,CH=NOH
The primary and secondary nitroparaffins react with nitrous acid to form alkyl nitrolic acids and alkyl pseudonitroles, respectively: CH&HzNOz
+ HKOz
--j
,NO* CHaC \XOH
+BO
(ethyl nitrolic acid)
YO2
(CHJzCHN02
+ HSOn +(CHJaC(so+ Epseudonitrole) L0 (propyl
Since solutions of alkali salts of nitrolic acids are red and of pseudonitroles blue, the reaction with nitrous acid is used to distinguish between primary, secondary, and tertiary alcohols. These are converted first to iodides and then to nitroparaffins. Since tertiary nitroparaffins do not react with
The primary and secondary nitroparaffins combine with formaldehyde in the presence of an alkaline condensing catalyst such as sodium carbonate. The number of moles of formaldehyde which can be combined with a nitroparaffin is eaual to the number of hydrogen atoms which are attached tdthe same carbon as is the ni60 group. Thus nitromethane can react with three molecules of formaldehyde, nitroethane and 1-nitropropane with two, and 2-nitropropane with one: CHsNOz + 3HCHO --f (CHzOH)3CKOz CHSCHINO~+ SHCHO +(CHz0H)zCNOz-CHs CHsCHzCHzNOz BHCHO + (CHzOH)zCNOz-CH,CH, (CH3)ZCHNOZ + HCHO + (CH20H)CNOz-(CHa)z
+
Although higher aliphatic aldehydes also can be combined with nitroparaffins, it appears that only one molecule will react, regardless of which nitroparaffin is used.
Reactions of this type are not limited to the aliphatic aldehydes. Sromatic compounds such as benzaldehyde give similar reactions. Kitroethane and benzaldehyde form 1phenyl-2-nitro-1-propanol and its dehydration product, 1phenyl-2-nitro-1-propene : CeHsCHO + CHsCHzNOz+CsH&HOH-CHNOz-CHs+ CsHsCH=CNOr-CHz HzO
+
I n general, the aldol condensations produce nitrohydroxy compounds in which the hydroxyl radical is attached to a
INDUSTRIAL AND ENGINEERING CHEMISTRY
JULY, 1940
FIGURE 3.
2-NITROPROPAXE
891
TREE
CHsCHNOzCHa
carbon adjacent to the one to which the nitro group is combined. This holds true for the nitroglycols as well as for the nitroalcohols. Chlorinated aldehydes may also be used for producing nitroalcohols containing a chlorine group. The nitrohydroxy compounds can be esterified with many of the organic and inorganic acids. On nitration the tris(hydroxymethy1)nitromethane reacts similarly t o glycerol and forms a trinitrate. This product has been found to be an excellent explosive. The nitroalcohols can be dehydrated to form nitro olefins. Reaction may be brought about either by treating a nitroalcohol with a dehydrating material such as zinc chloride or by reacting an ester of the nitroalcohol with sodium carbonate.
methyl-l,3-propanediol to 2-amino-2-methy1-lj3-propanediol, and 2-nitro-2-methyl-1-propanol to 2-amino-2-methyl-1-propanol. Aminohydroxy compounds of this nature form organic soaps when mixed with higher fatty acids such as oleic or stearic. These soaps are excellent emulsifying agents. On heating such soaps, amides are formed:
+RCONH-C(CHzOH)3
RCOOH-NH?C(CH,OH),
The aryl alkyl nitroalcohols and nitroolefins react similarly to the aliphatic nitrohydroxy compounds. Thus the 1-phenyl-2-nitro-1-propanol may be reduced to l-phenyl-2amino-1-propanol, and 1-phenyl-2-nitro-1-propene to 1phenyl-2-aminopropane, the salts of which have pharmaceutical uses.
Aminohydroxy Compounds
Chlorinated Products
The nitrohydroxy compounds are reduced by hydrogen or other reducing agents to the corresponding aminohydroxy compounds. Thus the tris(hydroxymethy1)nitromethane is reduced to tris(hydroxymethyl)aminomethane, 2-nitro-2-
Chloronitroparaffins may be formed by chlorinating the sodium salt of a nitroparaffin. When chlorination is carried out in this way the chlorine attaches itself to the same carbon atom with which the nitro group is combined. There-
TABLE11. PHYSICAL CONSTAKTS OF NITROPARAFFIN DERIVATIVES 2-Sitro-1-butanol NO, Formula
Mol. weight Melting point O C. Boiling point 6t 10 mm., C. p H 0.1 M aqueous soin. Soly. in 100 cc. water a t 20' C , grams
CH~AHICHCHZOH 119 -47 t o - 4 s 105 4 51 20
2-Amino-1-butanol 2"
Formula
2-Nitro-%methyl- 2-Kitro-2-methyl-l,31-propanol propanediol NO? SO* CH~CHIOH 119
bHs
90-9 1 94 5-95 5
5 12
350
CH20HkCHzOH CH3
135 147-149 Decomposes 5 42 80
2-Amino-2-methyl- 2-Amino-2-inethyl1-propanol 1,3-propanediol NHz "*
2-Nitro-Z-ethyI-1,3propanediol NO? CH~OH&CHIOH C?Ha
149 56-57 Decomposes 5 4s 400
Tris(hydroxymethy1) nitromethane NOzC(CHz0H)a 151 165-170 Decomposes 5 61 220
2-4mino-2-ethyl-1,3- Tris (hydroxymethyl) aminomethane propanediol SHz
I
CHadHzCHCHzOH
CHa&CH*OH
CH?OH~CHIOH
CHIOHCCH~OH
0.5 164 1.453
miscible 1 153 1.449
... ...
is6
NHd2(CHiOH)a
Mol. weight Melting point, C. Boiling Doint. C. A t Ib'mm. Specific gravity H 0.1 M soln. a t 20' C. oly. in 100 cc. water, grams
b
Vapor pressure a t 20" C (estd.) m m Flash point, Tegliabue :pen cu;, O F.' Index of refraction, 20° C.
...
miscible 1 490
...
... ...
fore the number of chlorine atoms which combine Kith a given nitroparaffin is the same as the number of moles of formaldehyde which will react with the same nitroparaffin to produce a nitrohydroxy compound. Thus nitromethane can add three chlorines, nitroethane and 1-nitropropane two, and 2-nitropropane just one. The product produced by the complete chlorination of nitromethane in the presence of calcium carbonate or from the alkali salt is known as chloropicrin. This product was used as a gas in the first World War. It is an excellent ground larvicide and is effective in the control of rodents in city dumps. Chloropicrin is reacted with sodium ethylate to produce ethyl orthocarbonate and with ammonia to produce guanidine : Cc1,NOz 4CzH,ONa+ (C&0)4C xaNOz f 3SaC1 ISH3 CClaNOz + HN\’=C(NHz)z
+
+
Miscellaneous Reactions of Nitroparaffins A few of the other reactions of the nitroparaffins will indicate the numerous possible applications of these products both in research and industry. The potassium salt of nitroethane combines with diazobenzene nitrate to yield nitroacetaldehyde hydrazone (1) : CH&( NOz)=N--I\THCeH, If reacted with benzoyl chloride, alkali salts of nitroethane yield benzoyl acetohydroxamic acid (4):
The reaction between nitroethane and ethylzinc results in the formation of P-ethyl-P-sec-butyl hydroxylamine ( 5 ) . Mercury fulminate is the product obtained when mercuric chloride and sodium nitromethane are reacted together (6) : 2CHzNOzNa HgC12+ (C=N0)2Hg 2Hz0 2NaC1
+
+
+
Nitromethane can be condensed with ketones to yield dinitro compounds (8) :
The action of acetic anhydride on aldoximes results in the formation of nitriles and on ketoximes yields acetates : RCH=NOH +RC=K RR’C=XOH +RR’C=NOCOCHI Monosubhtituted acid amides result when ketoximes are treated with such products as acetyl chloride, phosphorus trichloride, and boron fluoride : RR’C=?;OH
+RCONHR’ + R’COXHR
Aldoximes can be oxidized with persulfuric acid to form hydroxamic acid: NOH RCH=SOH-RC[
‘OH
The reaction of nitrosobenzene and hydroxylamine in the presence of an alkali‘yields an alkali salt of benzene diazotate. This product can be used as a starting point for the production of azo dyes, phenylhydrazine, and many other complex organic chemicals: CeHjSO
+ KH2OH + KOH +CeHfiN=SOK + 2Hz0
Dimethylglyoxime is prepared by first making the isonitroso compound from methyl ethyl ketone and nitrous acid and reacting this with hydroxylamine: HNOz
+
CH3COCzHj
CH,C=NOH I CH3C=0
NHzOH
CH@=NOH cH/c=NoH
An old process (for which patents have expired) relates to the use of hydroxylammonium salts in the production of indigo. The hydroxylamine is reacted with aniline and chloral to form the intermediate product, isonitrosodiphenylacetamidine. On treatment of this product with sulfuric acid, isatin a-anilide is formed: 2CeHjNHz
+
CClaCHO
+ NHZOH + CBHjNH-C-CH=T\TOH
HzS04
+
Dinitro compounds can also be produced by bringing together a chloronitroparaffin and the sodium salt of the nitroparaffin: CHzNOzNa CH3CHC1NO~+CH3CHNO~-CH2NO2 NaCl
+
+
Hydroxylamine Much has been written about hydroxylamine, one of the most reactive reagents. Since the product contains no carbon, like ammonia it is classified as an inorganic material. Hydroxylamine must now be considered as a derivative of the nitroparaffins. The uses of this old chemical have been extremely limited because of its high price. The nitroparaffin development is changing this situation, and many old reactions are being reviewed by industrial chemists to determine whether they may now be commercially exploited because of the availability and greatly lowered prices of hydroxylammonium salts. Hydroxylamine combines with aldehydes and ketones to form aldoximes and ketoximes, respectively. On reduction the oximes yield the corresponding amines:
+ NHzOH +RCH-XOH + ”$OH +RR‘C=KOH
RCHO RR’CO
Hz Hz
RCHzNHz
+RR’CHNH2
Hydroxylamine reacts with hydrocyanic acid t o form formamidoxime, an isomer of urea: HCS
+ NHzOH +H N S H N H O H
The pyrrole ring is opened by the reaction of hydroxylamine. The reaction results in the formation of the dioxime of a succinic aldehyde: g:ZZE>H
+
HON=CH(CH.JzCH=NOH
Literature Cited (1) Bamberger, E., Ber., 31, 2626 (1898). (2) Fraser, H. B., and Kon, G. A. R., J. Chem. Soc., 137, 604 (1934). (3) Hoffman, Eduard, and Meyer, Victor, Ber., 24, 3528 (1891); Meyer, Victor, Ibid., 24, 4243 (1891). (4) Jones, Lauder W., Chem. Zentr., 1898, I, 564. (5) Mamlock, L., and Wolffenstein, R., Ber., 34, 2500 (1901). (6) Xef. ,J. U., .4nn.. 280, 275 (1894).
