tents are washed into a 150-ml. beaker containing 10 to 15 drops of dilute hydrochloric acid, 0 . W . The solution is boiled for 1 minute to remove carbon dioxide, cooled, and titrated. No appreciable amount of boric acid is lost if the boiling time is extended 2 or 3 minutes. Standard 0.03 to 0.04N carbonate-free sodium hydroxide is used for the titration. The end point is taken as the intersection of the p H us. volume curve with a parallel line midway betxeen two parallel tangents. When the strong acid has been neutralized, about 10 grams of mannitoI is added and the titration is completed. The final end point is determined graphically as described above. Table I1 shows results obtained on a variety of boron-containing compounds. These compounds were mostly research samples, but they were considered to be pure, a n acceptable assumption in most cases since the samples were recrystallized, sublimed, or run through some other purification step prior to analysis. The standard deviation is
Table 111.
Analysis of Phosphorus and Fluorine Compounds
(Carius tubes appeared to be etched after oxidation of samples containing fluorine) Boron, yo Compound Calcd. Found ( CnHo)J’BH3 5.01 3.26 (CdH$)aPB(C Z H S ) ~
3.60
(C~L)~PBHJ BloH1,(NaF added)
3.92 88.46 8.52
1.88 3.96 4.46 2.87 147.98 120.08 10.16 12.01 ~________
=t0.33% absolute.’ A majority of the analyses were above the theoretical values indicating a possible bias in the method. This may be due to leaching of boron from the borosilicate glass Carius tubes during the oxidation. Fourteen analyses performed on a sample of HiCal, a boron-based high
energy fuel, averaged 62.56 & 0.35%. Eighteen macro Carius analyses of the fuel gave an average of 62.6% boron. Six boron analyses per day can be performed by one operator. Phosphorus and fluorine interfered in the determination of boron by this method. Table I11 shows results of boron analyses performed on samples containing these elements. LITERATURE CITED
(1) Callery Chemical Co., Callery, Pa., unpublished data, 1954. (2) Carius, L., Ann. 116, l(1860). ( 3 ) Xederl, J. B., Xiederl, V., “Organic Quantitative Microanalysis,” 2nd ed., pp. 151-7, Wiley, Kew York, 1942. ( 4 ) Schlesinger, H. I., Brown, H. C.. Horvitz, L., Bond, A. C., Tuck, L. D., Walker, A . O., J . Ana. Chem. SOC.75, 222 (1953). ( 5 ) Wartik, T., Schlesinger, H. I., Ibid., 75,835 (1953).
RECEIVED for review October 18, 1960. Accepted March 20, 1961.
Reduction of gem-Dinitro and Trinitro Compounds with Tita nium(III) ChIo rid e MAE I. FAUTH and GEORGE W. ROECKER Research and Development Department, U. S. Naval Propellant Plant, Indian Head, Md.
b The reduction of three classes of nitro compounds b y titanium(ll1) chloride has been investigated, to determine the feasibility of this reaction for assay of these materials. For the gem-dinitro compounds 2,2-dinitropropane and 4,4-dinitropentanoic acid, one nitro group, corresponding to six equivalents of titanium(lll), is reduced. For the compounds with three nitro groups on a terminal carbon, such as trinitromethane and 2,2,2-trinitroethanoIr two nitro groups are reduced, consuming 1 2 equivalents of titanium(ll1). For the aromatic compound 2,4,6-trinitromesitylene, the expected 18 equivalents are required. High results are obtained for 1,3,5-triazid0-2,4,6-trinitrobenzene, probably because of partial reduction of the azide groups. When the conditions of the reaction are controlled, reproducible results may b e obtained.
T
HE reaction of titanium(II1) chloride with aromatic nitro compounds is well known. For nitroparaffins and their derivatives Rodd (9) has proposed the following reaction:
RCN(N02)Z 4 ”,OH
+ RCH=NOH +
RCHzNH,
The purpose of this investigation was 894
ANALYTICAL CHEMISTRY
to determine to what extent gem-dinitro compounds and trinitro compounds which have all three nitro groups on the same carbon are reduced by titanium (111) chloride and whether suitable analytical methods for this type of compound could be devised using this reaction. The compounds used were 2,2-dinitropropane, 4,4-dinitropentanoic acid, trinitromethane, 2,2,2-trinitroethanol, 1,3,5-triazido-2,4,6-trinitrobenzene, and 2,4,6-trinitromesitylene. The techniques of handling titanium (111) solutions and their application to the determination of nitro grcups have been described by Kolthoff and Belcher (6)* Methods for the reduction of aromatic nitro compounds with titanium(II1) have been discussed by Becker and Shaefer ( I ) , who give extensive references to the literature. EXPERIMENTAL
Materials and Reagents. The four compounds not commercially available were supplied by t h e Organic Division and may be synthesized by t h e following routes. 4,4-Dinitropentanoic acid may be obtained by the method of Schechter and Zeldin (IO), which involves the
reaction of 1-1-dinitroethaneuith potassium hydroxide to form the potassium salt, which reacts with methyl acrylate to yield methyl 4,4-dinitropentanoate. Hydrolysis of the methyl ester provides the 4,i-dinitropentanoic acid. Trinitromethane. A convenient preparation is that of Ficheroulle and GayLussac (S), based on the Oxidation of acetylene with nitric acid. 2,2,2-TrinitroethanoI was described by Marans and Zelinski (6) and its preparation investigated by Ficheroulle and Gay-Lussac (4). Both used the reaction of nitroform and paraformaldehyde. 1,3,5 - Triazido - 2,4,6 - trinitrobenzene. Preparation and properties have been summarized by Davis ( 2 ) . The material used was obtained by nitration of 1,3,5-trichlorobenzene, followed by treatment with sodium azide. 2,2-Dinitropropane. A sample was supplied by Commercial Solvents Corp. 2,4,6-Trinitromesitylene, Eastman White Label, was used. ElementaI analyses were obtained for all of the compounds (Table I). Titanium(II1) chloride (Lallotte Chemical Co.) was purchased as the 209& solution and a 0.2,V solution prepared by adding 100 ml. of 37% hydrochloric acid to 150 ml. of the 20Yo titanium(II1) chloride solution and diluting to 1 liter. After dilution to approximate volume, the stock solution is deoxygenated by
passing a stream of car%on 4 o s i d e
through it for 20 minutcs. All operations arc performed in a closcd system under carbon dioside. Standardization of the solution is obtained by titration against potassium dichromate. Commercial stock solutions of titanous chloride may contain inore than 1% of iron(1Ii chloride as an impriiity. The effect and mrasurciiient of this inipurity arr discusscd by Picrson :tnd G:iiitz ( 8 ) . Proccdurc for correction is also drtailed in a military stand:trd ( 7 ) . This consists of adding 5 ml. of 207, NH4CKS solution to the end point of the above standardization. If this end point has not been overrun, :my iron(II1) present nil1 color the indicator an intense dark red. The quantity of iron present is then found by continuing the titration with Tic13 t o t'hcl disappearance of the red color. Pure TiC13 may be prepared in the laboratory from stable 'I'iHn, or by electrolytic rcduction of distilled TiC14. A stock concentrate preparrd by the second method is commercially avail:tble. Iron(II1) ammonium sulfate (Fisher ACS reagent grade) is prepared by dissolving SO grams of FeNH4(S0&.12H& in 500 ml. of concentrated sulfuric acid and diluting to 1 liter. This is standardized by titration against standardized titanium(II1) chloride solution and used as a secondary st'andard. Potassium thiocyanate (Fisher ACS reagent grade) is prepared as a 20% by weight solution. Procedure. Approximately 1 gram of t h e nitro compound is dissolved in LOO inl. of glacial acetic acid and t h e resulting solution transferred to a 500-nil. volumetric flask and diluted t o volume. Fifty-milliliter aliquots a r e taken for analysis. Carbon dioxide is passed into n two-necked 500ml. boiling flask attached t o a reflux condenser for 5 minutes while a 50-ml. d i q u o t of the sample and 10 ml. of the 0.21Y titanium(II1) chloride solution are added. The reaction mixture must be kept under carbcn dioxide until the titration is completed. The mixture is then boiled for 10 minutes and cooled to room temperature. Two milliliters of 20y0pot'assium thiocyanate solution are added and the sample is titrated with iron(II1) ammonium sulfate until the red color persists for more than 30 seconds. A blank of the materials and boiling time must be run daily. Compound 2,2-Dinitropropane 4,4-Dinitropentanoic acid 'hinitromethane 2,2,2-Trinitroethanol
Alolecular Weight 134 09 192 13 151 04 181 07
1,3,5-Triazido-2,4.G-trinitro-
benzene
2,4,G-Trinitromesit3.lene
336 16 255 19
RESULTS AND DISCUSSION
The results obtained by this method are gii-en in Table 11. For. the gem-
Table I.
Elemental Analyses of Compounds
%C %H _____ %N Calcd. Found Calcd. Found Calcd. Found 26.87 27.70 4.51 4.58 20.90 .. ~. ~. 19.33 ~.-~ 31.26 30.91 4 . i 9 4.16 14.58 14.45 13.27 13.18 1.67 1.69 23.21 22.80 7.95 7.71 0.67 0.75 27.82 26.99 2,4,6-Trinitromesitylene 42.36 42.32 3.55 3.23 16.46 16.10 1,3,5-Triazido-2,4,6-trinitrobenzene21.43 21. 74 . . , . . . 50.00 49.38
Compound 2,BDinitrourouane 4;4-Dinitrope~tanoicacid 2,2,2-Trinitroethanol Trinitromethane
Table II.
~
Equivalents of Titanium(ll1) per Mole of Nitro Compound KO.of
Compound 2,2-Dinitropropane 4.4-Dinitronentanoia ~-~~~ acid 2,2,2-TrinitroethanoI Trinitromethane ~A
1 5.44
Replicate S o . 2 3 4 5.51 5 . 5 1 5.40
5 5.48
Nitro Groups Std. ReAv. Dev. duced 5 47 0.048 1
~~
2,4,6-Trinitromesitylene
1,3,5-Triazido-2,4,6trinitrobenzene
5.96 5.93 5.99 5.99 6 . 0 0 5 9 7 0.029 11.92 11.61 11.63 11.76 11.73 11.73 0.124 11.69 11.73 11.36 11.94 11.77 11.80 0.212 18.12 18.13 18.00 18.05 18.03 18.07 0,057
2 2 3
19.75 19.16 19.78 19.53 19.62 19.62 0.139
3
dinitro compounds titanium(II1) chloride can be expected to reduce only one of the nitro groups present. For 4,4dinitropejitanoic acid, n-liich was known to be a pure compound, a n average value of 5.97 equivalents of reducing agent per mole of compound was obtained. For 2,2-dinit'ropropane the value was 5.47. The estimated purity of the compounds on the basis of the micro-Dumas and titanium(II1) methods is shown jn Table 111. Since the micro-Dumas as performed in our laboratory generally yields slightly lower than theoretical values for compounds of the types considered, estimat'ed purity based on the nitrogen content alone is probably somewhat low. For the gem-dinitro compounds a study vias made of the effect of changing various conditions of the reaction. The reaction was found to be sensitive to the total amount of acid present, since too little acid results in hydrolysis of the tit'aniuni(II1j solution, and too much inhibits the reaction. For 2,2dinitropropane a -ariation in conditions gave the results shown in Table IV. The modifications tried were found to be less reproducible than the indicated method, and the presence of sodium acetate ])reduced foaming. Attempt's t o reduce 2-nitropropane by the iiictliotl used for the gem-dinitro compounds gal-e valuts of 1.2 to 4.0 equivalents of titaniwn(II1) per niole of compound. 3Iicroanalysis of 2-nitropropane indicnted 9;.2c0purity. For 4,klinitropentanoic acid doubling the amount of acid held the number of equivalents of reducing agent consumed to 5.8, even after refluxing for 30 minut'es. Increasing the reflux t,ime about 10 minutes had little effect,
Table 111.
1
Estimated Purity of Compounds
% Purity NicroDumas
TCI, reduction 92 5 99.8
97.0 98.2
98.3 97.8
98 0
100 0
Compound 2,2-Dinitropropane 92 5 4,4-Dinitropentanoic 99 2 rlrirl
TrT&omethane 2,2,2-Trinitroethanol 2,4,6-Trinitromesitylene lj3,5-Triazido-2,4,6trinitrohenzene Interference from
109. Z5 azide groups. 08.8
Table IV. Effect of Varying Conditions of Reaction on Reduction of 2,2-Dinitropropane
Treatment Dilute with 50 ml. of 57c acetic acid Omit addition of 5 nil. of 6.47 hydrochloric acid Both of above Substitute 10 ml. of 10% sodium acetate for hydrochloric acid Substitute 5 mi. of 10% sodium acetate, reflux for 5 minutes .4dd two selenized Hengar granules
Equivalents/ Mole
5.32 5.90 5.30 6.24 5.93 5.21
uliile refluling less than 10 minutes gave erratic results. For the trinitro coinpounds the results indicate that two nitro groups are reduced, involving 12 equixalents of titaniuni(lI1) per mole. For the aromatics the evpected reduction of all three groups is obtained. For 2,4,6-trinitromesitylene, which contains no other functional group capable of being VOL. 33, NO. 7, JUNE 1961
895
reduced, 18 equivalents are required. For 1,3,5triazido-2,4,6-trinitrobenzene the value of 19.62 indicates partial reduction of the azide groups. Although the end products have not been identified, reproducible results may be obtained with this method for the determination of nitro groups in gemdinitro and in trinitro compounds on the basis of the following assumptions: R-C( NOl)*-R R-C(NOJ1
+ 6e + 12e
+
R-C( NOz)- R
I
"9 +
R-C(NH2)*
1
NO2 R
R
If these values are used for the number of equivalents of titanium(II1) ,onsumed per mole of nitro compound, this method is suitable for the assay of such compounds. The reason why all of the nitro groups are not reduced is under investigation. Since the transition from nonexplosive to explosive compound often occurs when the third nitro group is introduced into a compound, impact sensitivity
Table
V.
Impact Sensitivity of Compounds
Compound 2,2-Dinitropropane 4,bDinitropentanoic acid
Height, Mm. Failed at 600 Failed a t mn
Trinitromethane
LITERATURE CITED
"V"
2,2,2-Trinitroethanol
2,4,6-Trinitromesitylene 1,3,5-Triazido-2,4,6trinitr+
benzene Reference compounds for apparatus Nitroglycerin Tetryl Trinitrotoluene 5-kg. weight used for all tests.
600
300 100
100
250 600
in a steel cup, self-heating of the sample began a t about 85" C. and a t approximately 125" C. the compound -underwent a violent detonation, destroying the steel container and shearing off the connecting thermocouples. For safe storage this compound should be kept covered with water.
+
(1) Becker, W. W., Shaefer, W. E., "Determination of Nitro, Nitroso, and
Nitrate Groups,') in "Organic Analysis," Vol. 11, pp. 73-7, Interscience, New York, 1954. (2) Davis, T. L., "Chemistry of Powder and Explosives," pp. 436-8, Wiley, New York 1956. (3) Ficheroulle, H., Gay-Lussac, A,, M h . poudres 34,55 (1952). (4) Ibid., p. 121. (5) Ko!thoff, I. M., Belcher, R., "Volumetric Analysis," Vol. 111, pp. 610-19, Interscience. New York. 1957. (6) Maram, N.S., ZelinsG, R. P., J . Am. 72, 5329 (lg50). (7) Military Standard MIL-STD-286, Method 601.1, J~~~28, 1956. (8) Pieraon, R. H., Gantz, E. C., ANAL. CHEM.26,1809 (1954).
tests were run on all six compounds (Table V). Trinitromethane, although not shock-sensitive, has been known to undergo spontaneous detonation when stored in the solid state. For the other three compounds the order of increasing ( g ~ ' c o " m o , " ~ ~ 2 1 " d s , H ~ ~ ~ c ~ sensitivity to detonation by impact is N~~ Yo&, 1951. 2,2,2-trinitroethanol, 2,4,6-trinitromesit(10) Schechter, H., Zeldin, L., J . Am. ylene, 1,3,5-triazido-2,4,6-trinitrobenChem. SOC.73, 1276 (1951). when Go mg* Of the azido cornRECEIVED for review December 19, 1960. pound were heated a t 2" C.per minute Accepted April 5, 1961.
Use of Differential Reaction Rates to Analyze Mixtures of Organic Materials Containing the Same Functional Group Application to Mixtures of Alcohols Including Mixtures of Isomeric Primary and Secondary Alcohols and to Mixtures of Aldehydes and Ketones SIDNEY SlGGlA and J. G O R D O N HANNA Olin Mathieson Chemical Corp., 275 Winchester Ave., New Haven 4, Conn.
b Many reactions involved in organic analysis via the functional groups are second-order reactions. Proper choice of reaction conditions and plots of reaction rate data in the standard linear plot for second-order reactions makes possible analysis of mixtures of organic materials containing the same functional group. The linear secondorder plot contains a straight-line portion for each component in the mixture, from which the composition of the mixture can b e computed. Two functional-group analytical systems are shown to which the rate approach was applied-alcohol mixtures and mixtures of carbonyl compounds. 896
ANALYTICAL CHEMISTRY
T
HE same functional group on different organic molecules often exhibits differences in its rate of reaction with a given reagent. This difference in reaction rate can be due to the size and configuration of the molecule onto which the functional group is attached, or to the effect of substituents on the organic molecule. It is apparent that this difference in reaction rate might form the basis for a system of analysis which could differentiate between components in an organic system. Lee and Kolthoff (11) pointed out the potentialities of this approach and made some attempts to utilize reaction rates to analyze some mixtures.
A system of analysis is presented here which utilizes reaction rates to analyze mixtures of organic materials containing the same functional group. The approach used is different from that used by Lee and Kolthoff and has certain advantages, especially in termi of range of applicability. The approach described below uses the conventional plotting of secondorder reaction data. A second-order reaction is one where the rate is dependent on the concentrations of two reactants in the system. Hence, if A and B are reacting, their concentrations, a and b, determine the rate. If 2 describes the amount of A
