only the sulfhydryl form enters into the chemical reactions under consideration here. IDENTIFICATION OF BARIUM SULFATE
Barium sulfate can be detected through the Tohlers effect provided no other sulfate is present. The test is based on conversion into barium carbonate and reprecipitation of violet barium sulfate in the presence of potassium permanganate. Procedure. A tiny portion of the test material is placed in a micro crucible along with 1-2 drops of 10% sodium carbonate solution. The suspen5ion is taken to dryness and ignited gently (BaSO1 Sa2C03-+ SazSOl DaCO3). The cooled mass is treated in succession with a drop of the permanganatebarium chloride solution, a drop of hydrochloric acid ( 1 : 5 ) , and a drop of 20%-hydrosylamine hydrochloride solution. A positive response is indicated by a violet residue.
+
+
IDENTIFICATION O F BENZIDINE SULFATE
Benzidine sulfate is only slightly soluble in water and dilute acids. It behaves toward potassium permanganate-barium chloride solution in the same manner as does strontium and calcium sulfates. Consequently, if the procedure given for CaCOl is followed, it is possible to detect the sulfuric acid bound to benzidine. Xinimal amounts of the test material suffice. As a supplementary, sensitive test for benzidine, use can be made of the reaction of sodium rhodizonate with benzidine salts; a violet precipitate results ( b ) . This reaction occurs likewise with benzidine sulfate. I t may be accomplished by treating a tiny portion of the solid on filter paper or a spot plate with a drop of a freshly prepared 1%water solution of sodium rhodizonate. It may be expected that reactions of organic sulfur compounds that yield sulfate ions can be detected through the Wohlers effect and that tests for such
compounds can be based on this effect. Studies along these lines are now in progress. LITERATURE CITED
(1)Beilstein, “Handbuch der Organischen
Chemie,” Band 111, p. 182, Berlin,
1921. (2) Feigl, F., “Chemistry
of Specific, Selective, and Sensitive Reactions,” p. 442, Academic Press, New York, 1949. (3)Feigl, F., “Spot Tests in Inorganic Analysis,” 5th ed., p. 470, Elsevier, ilmsterdam, 1958. (4) Feigl, F., “Spot Tests in Organic i\nalysis,” 6th ed., Chap. 3, Elsevier, Amsterdam, 1960.
(5)Ibid., p. 437. 16) Feiel. F.. Aufricht. W.. Rec. l’rac. Chim’: 58, 1127 (1927j. (7) Maly, R.,Jlonatsh. 11, 278 (1890). (8) Wohlers, H. E., Z. .Inorg. Allgem. Chem. 59, 203 (1908). (9)Yagoda, H., J . Znd. Hyy. Toricol. 26, 224 (1944). \
I
RECEIVEDfor review LIarch 4, 1964. Accepted April 14, 1964. The authors are indebted to the Conselho Sacional de Pesquisas for financial aid in this research.
Determination of Isomer Distribution Ratio in Mixtures of the Monoisobutyrates of 2, 2, 4-Trimethyl-1, Spentanediol by Nuclear Magnetic Resonance HORACE F. WHITE, CHARLES W. DAVISSON, and VICTOR A. YARBOROUGH Research and Development Department, Union Carbide Corporation, Chemicals Division, South Charleston, W. Vu.
b Nuclear magnetic resonance (NMR) techniques have been used to analyze mixtures of the monoisobutyrate isomers of 2,2,4-trimethyl-1,3-pentanediol. The NMR technique was chosen because it permits analysis of such mixtures without calibration standards. The NMR spectrum is assigned and, as an example, a commercially available mixture is analyzed. The commercial sample used contains about 40% secondary ester-primary alcohol and 6OY0 primary ester-secondary alcohol.
T
HE
PARTIAL
ESTERIFICATION
Of
2,2,4 - trimethyl - 1,3 - pentanediol with isobutyric acid yields three chemical entities, the diester and two monoesters. While the diester is sufficiently high boiling to enable the two monoesters to be separated from it by distillition, the mixture of monoesters, is not easily rectified. K e are interested in measuring the concentration of the secondary ester-primary alcohol comi~onentof this binary mixt1.ii-e (such a hinary mixture is currently marketed t)y Tennessee Eastman Chemical C‘o. as ’I’cwnol) because it may be used as an
intermediate to other more useful materials. The Xh4R technique was chosen to characterize the isomers and analyze the mixture because, unlike other instrumental techniques, no pure reference materials are required for calibration, particularly on binary mixture analysis. EXPERIMENTAL
Binary mixtures of the monoisobutyrates were obtained from Tennessee Eastman Chemical Co. and by synthesis in our laboratories. S l I R spectra were obtained with a Varian -\ssociates AX-60 spectrometer. Spectra were measured of CC1, solutions containing various (see results) concentrations of the mixture and about 1.0% of tet,ramethylsilane. I n addit,ion, some of the commercial material was acidified with hydrochloric acid vapor before scanning, and a second portion of it was also exchanged with D,O prior to NMR scanning. RESULTS A N D DISCUSSION
Before mixtures can be analyzed for their components, the NMR spectrum must be assigned, and chemical shifts
Table I. Observed Chemical Shifts and Group Resonance Assignments for Texanol”
Group Methyl ( 3 types) Methme, pentane Methine, butyrate Methylene adjacent to alcohol Methine adjacent to alcohol Alcohol OH LIethylene adjacent to ester Methine adjacent to ester
Chemical shift3
Assignmentc from figure
1 0 1 9 2 4
la la la, 2, and 3
3 2
la, 2, a n d 3
3 4
lband 2a
3 9
2 and 3
4 8
2 and3
a A mixture of the two monoisobutyrate isomers of 2,2,4-trimethyl-1,3-pentanediol: registered I:. S. trademark of Tennessee Eastman Chemical Co. These values are the nominal resonance position (see spectra) in parts per mil!ion from tetramethylsilane, internal standard. As seen in Figures 2 and 3, these values vary with concentration. Assignrnents are in agreement with general group region as indicated by references ( 1 - 3 ) .
VOL. 36, NO. 8, JULY 1964
1659
characteristic of each portion of the mixture must be discovered. The spectrum of a typical mixture is shown in Figure la, and Figures 16 and 2a show the effect of acidifying the material and exchanging it with D 2 0 ,respectively. Figures 2 and 3 show the effect of dilution by an inert solvent (CC1,) on the D20-exchanged materisl. From these data it is possible to assign the spectrum to the two isomeric species found in this mixture; however, to simplify the discussion, diagrams of the two isomers are presented.
H
H CH3H I l l 1 CH,-C-C-C--C-O-C-C-CH3 1 1 1 1 CH3 OH CH3 H H H CH3 H , I
I
'
I
I
1
CH~-C-C-C-C-OH
Before considering the methylene resonance patterns in detail, discussion of methyl resonance peculiarities is needed. Two pairs of doublets with doublet separation of about 7 cycles per second are easily identified, and they probably arise from the isobutyl methyl groups. There is no strong, single line representing the 2,2-dimethyl protons; however, with two isomers present, these methyl resonances might not superimpose. Perhaps the absence of a single strong peak indicates that these methyl groups are not freely rotating,
O H
I1
I
Primary ester-secondary alcohol
1
CH3
I
Secondary ester-primary alcohol
~
CH3 0 CH3 H O=C
I
H
\I
C-CH3
I
CHB Table I presents our assignments which are in agreement with those in the current literature (1-3). While the various bands are readily assignable from their spectral position, a discussion of the methylene resonances is in order.
TEXANOL AS RECEIVED
and this restricted rotation causes a splitting of the single line into two or more components for each isomer (4). The complex structure of the methyl
resonances, while not completely under stood, is not unexpected. Furthermore a complet,e understanding of these resonance patterns is not essential for the desired analysis. Ambigities in t'he methylene resonances are somewhat resolved by consulting the dilit,ion spectra. The methylene protons adjacent to the esterified primary alcohol group (3.9 p.p.m.) exhibit the characteristic four lines of an A B pair ( 5 ) . The nonequivalznce of these two protons probably arises from the hydrogen bonding of one of t'hem to either the ester carbonyl or the secondary alcohol oxygen while the other is frze to int,eract with the solvent. One proton apparently does interact' with the solvent becaus? the band center moves downfield on dilution to the same degree as the band center of the methine proton adjacent to the esterified secondary alcohol (4.8 p.p.m.). The methylene protons adjacent to an alcohol group have a resonance pattern similar to their ester counterparts. examination of Figure 36 shows that the group a t 3.2 p.p.m. is composed of a t least four lines and perhaps the expected six (four from the A B psir of the primary alcohol methylene and two from the secondary alcohol methine which has one adjacent proton)
A
I
I
B
30% TEXANOL IN CC14
I
8.0
,
,
,
4.0 3.0 2.0 1.0 CHEMICAL SHIFT (PARTS PER MILLION PARAMAGNETICALLY FROM TETRAMETHYLSILANE. INTERNAL STANDARD), 60
70
Figure 1 .
5.0
Texanal as received b. Acidified Texanol (HCI/H*O vapor) y-axis units a r e arbitrary spectral amplitude
e
1
Nuclear magnetic resonance spedrum of Texanol 0.
1660
I
0
ANALYTICAL CHEMISTRY
I
I
I
I
6.0 50 4.0 30 2.0 1.0 CHEMICAL SHIFT (PARTS PER MILLION PARAMAGNETICALLY FROM TETRAMETHYLSILANE. INTERNAL STANDARD).
8.0
7.0
, I 0
Figure 2. Dilution effects in the NMR spectrum of D,O exchanged Texanol 3.2, 3.9, and 4.8 p.p.m. resonances enlarged and expanded a.
100% Texonol
b.
30% Texanol in CC14
y-axis units a r e arbitrary spectral amplitude 4.8 p.p.m. resonance shifted b y 200 c.p.s. 3.9 p.p.m. resonance shifted by 1 5 5 C.P.S. Sweep width is 100 c.p.s. for shifted resonances
e
within 1% of the contained isomer concentration. To be sure that no diisobutyrate is present,, a check integration of all protons is made. From the int,egral amplitude per proton determined from the 18 methyl protons and the previously determined isomer concentrations, an integral amplitrtde for each isomer a t its characteristic resonance may then be calculated and compared with the observed amplitude. Such a compari~on is presented in Table I11 for the commercial mixt.ure. These data indicate that our sample of Texanol is a mixture of 41% secondary ester-primary alcohol and 59% primary ester-secondary alcohol.
I
20% TEXANOL IN CCIA
1070 TEXANOL IN CC14
LITERATURE CITED
I
7.0
80
60
I
I
5.0
4.0
I
I
1
2.0
3.0
(1) Dietrich, hI. W., Keller, R. E., ASAL. CHEM.3 6 , 258 (1964). (2) Meyer, L. H., Saika, A., Gutowsky, H. S.,J . Am. Chem. Sac. 75, 4567 (1953). (3) Nukada, K., Yamamoto, O., Suzuki, T., Takuchi, M.,Ohnishi, >I., AYAL. CHEM.35, 1892 (196.3). (4) Pople, J. A , , Schneider, W. G., Bernstein, H . J., "High-Resolution Xuclear hlagnetic Resonancte," p. 366, McGraw-Hill, Sew York, 1959. (5) Roberts, J. I),, "An Introduction to the Analysis of Spin-Spin Splitting in High-Resolution Suclear Magnetic Resonance Spectra," p. 56, \V.A. Benjamin, Sew York. 1961.
1.0
0
CHEMICAL SHIFT ( PARTS PER MILLION PARAMAGNETICALLY FROM TETRAMETHYLSILANE, INTERNAL STANDARD).
Figure 3. Dilution effects in the NMR spectrum of D,O exchanged Texanol 3.2, 3 . 9 , and 4.8 p . p m resonances enlarged and expanded a. 2 0 % Texanol in CC14 (3.1 p . p m resonance shifted b y 150 c.p.s.1 b. 10% Texanol in CCll y-axis units a r e arbitrary spectral amplitude 4 . 8 p . p m resonance shifted b y 2 0 0 c.p.s. 3 . 9 p . p m resonance shifted b y 155 c.p.r. Sweep width is 100 C.P.S.for shifted resonances
RECEIVEDfor review January 27, 1964. Accepted April 10, 1964. Table II.
Resonance, p.p.m.
Determination of Isomer Percentage
Integral Amplitude Amplitudea per proton
4 8 3 9
1 09 3 09
1 09 1 54
Isomer Structure
Per cent
11" ester, I " 01 I " ester, 11" 01
41 4 58 6
Amplitude measured in centimeters on original chart.
Correct ion Table 111.
Resonance, p.p.m. 1.0 3.9 4.8 Total
Integration of Texanol Spectrum
Integral AmpliTotal tude ampliper tude" proton 11.06 0 .i i c 0.26 14.15
0.615 ...
0:6i5
Calculated amplitude* ...
0.72 0.26 , .
a Integral amplitude measured in centimeters on original chart. * Calculated amplitude is isomer concentration times unit amplitude per proton as determined from 18 methyl protons times number of protons in structure contributing to resonance. Amplitude per proton obtained on a I h O exchanged sample and may be high as a result of nonexchanged 0-H.
A Computer Program to With a complete assignment of the spectrum and the discovery of isolated resonances characteristic of each molecular species (4.8 p.p.m. for secondary ester-primary alcohol and 3.9 1i.p.m. for primary ester-secondary alcohol), the individual isomer concentrations may be determined by integrating the intensities of the individual lines. Spectra of the D20-exchanged materials (similar to that presented in Figure 20) were used for integration. The concentration of individual isomers was det,ermined by integrating the 4.8-and 3.9-p.p.m. groups. Table I1 presents the determination of isomer percent in our sample of Texanol. Duplicate determinations indicate that the measurements are reproducible to
Optimize Times of Irradiation and Decay in Activation Analysis In this article by 1'.L. Isenhour and [;\N.~L. CHIX 36, 1089 (1964)] in Table I , Cases IVa and IVb, cross sections of 14-m.e.v. neutrons were erroneously used as input data with the fast fission neutron flux in computing the fast neutron reactions. The resulting data for these two cases, thercfore, do not reflect an experimentally feasible ana1y.k; however, thr (nomputations are correct with respect to the input data ured and still serve to illustrate the capabilitks of P R O G R A M
G. H. hlorrison
OPTIMIZE.
VOL. 3 6 , NO. 8 , JULY 1 9 6 4
1661
