the water vapor mass remains constant at any given temperature, and is independent of the total amount of combustion water produced (assuming the latter is sufficient to saturate the atmosphere). It follows that the proportion of water vapor in the vial rises as the total amount of water falls. If the higher temperature ranges are used for freezing, it would be wise to minimize the relative displacement loss, when very small samples are being assayed, by bringing the total weight of the charge to be burned to 6 mg with fuel (see below). The possibility of isotope being lost on the baskets, when they are shaken from the vials, has been investigated at count rates around 2000 cpm per burned specimen, and at a freezing temperature -85 "C. Provided baskets did not touch the ice in the vials, no increase over the background count was produced, when batches of 10 baskets were dropped directly into the scintillator solution. As no reason exists for thinking that baskets are preferentially dried, it is considered that the technique achieves virtually complete tritium trapping on the bottom of the vials. Because it is imperative that a gas-tight seal should exist between the foil of the cap and the vial neck, it is advisable to inspect the foil and the lip of the vial for imperfections before use. Pin hole openings in the former can be closed by routinely smearing the surface with heavy silicone oil; this has been shown to have no quenching effect. A smear around the lip also effects lubrication, and a better seal between glass and foil, when the cap is being tightly screwed home. In practice, baskets with shorter stems than those described by Gupta have practical and theoretical merits, First they are
more stable. Second they are cheaper, being made from about 9-cm wire. Third, the closer the burning specimen is to the bottom of the container, the longer it remains surrounded with oxygen undamped by the combustion products being formed. On trial the maximum amount of material (specimen, carrier cup, primer, and fuel) which could be burned was 7 mg, and for certain complete combustion, 6 mg. This figure is in agreement with that given by Kalberer and Rutschmann ( 5 ) using a 1-liter combustion flask--i.e., 1 mg per 4 ml of oxygen. As primer, carrier cup, and fuel amount to approximately 2 mg, samples should not exceed 4 mg dry weight. ACKNOWLEDGMENT
The author acknowledges with gratitude the every facility placed at his disposal in the Institut fur Krebsforschung der Universitat, Wien, by its Director, Professor Heinrich Wrba. T. H. VICKERS~ Krebsforschungsinstitut der Universitat 1090 Wien, Austria 1 Present address, Department of Pathology, University of Queensland, Medical School, Herston, Brisbane, 4006, Queensland, Australia
RECEIVED for review April 29, 1968. Accepted July 22, 1968. (5) F. Kalberer and J. Rutschmann, Biochemical Department,
Sandoz, Basel, supplied by Packard Instrument Co., Inc., U. S. A.,1967.
Automated Structure Elucidation of Several Kinds of Aliphatic and Alicyclic Compounds SIR: The automated data acquisition and computer-aided interpretation of spectra is rapidly expanding (1-3). For instance, the determination of the amino acid sequence in oligopeptides was accomplished by the computer interpretation of high resolution mass spectra (4, 5). Aliphatic saturated normal and monomethyl substituted hydrocarbons from C,to C ~were O also identified by computer-aided mass spectrometry (6). However, only one kind of spectrometer was tied into an electronic computer in every case. Here we wish to report an actual attempt to feed physical data, acquired via computers from WlS, NMR, IR, and UV, into a central computer which is programmed to structure elucidation based on a combination of all four types of data (Figure 1). The research up to date has been done with both aliphatic and alicyclic compounds containing less than fifteen carbons and only one oxygen, and with less than four sites of unsaturation. The whole system is composed of MS (JEOL, (1) D. H. Anderson and G. L. Covert, ANAL.CHEM.,39, 1288 (1967). (2) D. S. Erley, Presented at the Pittsburgh Conference on An-
alytical Chemistry and Applied Spectroscopy, Cleveland, Ohio, March 1968. (3) €3. P. Benz, Presented at 9th Experimental Nuclear Magnetic Resonance Conference, Pittsburgh, Pa., 1968. (4) M. Senn, R. Venkataraghavan,and F. W. McLafferty, J. Amer. Chem. SOC.,88, 5593 (1966). (,5,) K. Biemann, C. Cone, B. R. Webseer, and G. P. Arsenault, ibid., 5598. (6) B. Petterson and R. Ryhage, ANAL,CHEM., 39, 790 (1967).
2220
0
ANALYTICAL CHEMISTRY
+ I Autcmaric
Figure 1. System for automated structure elucidation JMS-OISG, Mattauch-Herzog type), NMR (JOEL, JNM-C60H), IR (Shimadzu IR-27G) and UV (Shimadzu MPS-SOL) spectrometers, four smaller computers (slave computers 1, 2, 3, and 4; JEOL, Science Master EC-1, binary 16 bits, 4096 words, arithmetic time 200 psec), and one larger computer (master computer, JEOL, JRA-5, binary 16 bits, 4096 words, arithmetic time 20 psec) with an outer memory to automatically elucidate the molecular formulas and partial structures of these compounds. The slave computer 1 connected with a comparater microphotometer (JEOL, JMA-1) calculates the possible combina-
Figure 2. A part of program resident on the master computer By this diagram the nature of methyl groups is clarified. CHsC, CHKH, CHsCH2, and CH3F represent methyl at tertiary carbon, methyl at secondary carbon, methyl at primary carbon, and methyl at olefinic linkage, respectively. Other abbreviationsare as follows: ME, presence of methyl group; UNS, degree of hydrogen demciency; NME, splitting number of methyl signal in NMR; and H16-19, presence of proton assigned as index 16-19. NMR spectrum is divided into about 30 regions and each of them is temporarily called “index” by the authors
MASS
DATA
NMR DATA
C
n
0
I NT
2 2 4 4 4 4 5 5 5 6 6 6 6
2 3 4 5 6 7 6 7 8 7 8 9 10
1
184 824 136 153 122 122 122 208 171 153 168 177 20 1
1 1
1 1
1
1 1 1 1 1 1 1
NO 1 2 3 4 5
6 7 8 9
POSI
I NT
369.6 368.4 367-0 137.2 128.0 126.4 124.2 113e4 112*0
35 43 30 I1 198 367 17 183 176
IR DATA
AREA 185 137 105 214 1014 1369 152 707 536
TOTAL AREA= 4419 NO 1 2
3 4 5
POS I 368*3 137.2 127.2 124.2 112*7
AREA 427 214 2383 15Q 1243
COUPLING JI. l . 2 < 3)
J= 1.2C 2 ) J= 1.2( 2 )
NO
POSI
1 2 3 4 5
3360 2984 2920 1714 1686 1614 1444 1378 1354 1268 1220 1162 ‘1066 1020 962 896 820
6 7 8 9 10 11 12 13 14 15 16 17
I NT 12 88 LO4 84 352 348 206 174 226 30 253 239 36 63 171 24 77
W DATA w POSI=4220
Figure 3. Reproduction of data computed by the slave computers for mesityl oxide (1) The upper part of NMR DATA stands for the digitalyzed NMR spectrum. In the second-step calculation, slave computer 2 searches for the peaks with same J values based on these data, then nine peaks are reduced to Rve peaks as shown in the lower part of NMR DATA. The numeralsin parentheses indicate the multiplicityof the peaks VOL. 40, NO. 14, DECEMBER 1968
2221
tions of carbon, hydrogen, and oxygen and the intensities of all mass fragments from mass spectrum recorded on a photo plate. All NMR signals-positions, intensities, and areasare digitalyzed through an analog-digital converter in slave computer 2. The coupling constant is also searched for by the slave computer. Each of the other slave computers (3 and 4)-those for the IR and UV spectrophotometers-determine positions and intensities of absorption bands. (The entire program resident on each computer will be reported in the near future.) All information thus given by the spectrom-
COMPOSI TION C( 6)H(10)0(
1)
FUNCTIONAL GROUPS COCC) CH=C C H 3 E F ) ( X 2 ) OR ( C H 3 C O C H 3 C F) CX 1 1
AND
CH3CF))
Figure 4. Reproduction of data computed by the master computer for mesityl oxide (1)
COMPOSITION COMPOSITION CC 5)HC 6)0( 1)
trans-Decaline (2) -
C( 10)HC 1 8 ) 0 ( 0 )
2-Methylfuran (5)
FUNCTIONAL GROUPS
FUNCTIONAL GROUPS FURANC2) CH3CF)CXl) ~~
~
COMPOSITION CC 7)H(10)OP
I
1)
3-Methylcyclohexenone (3: FWNCTIONAL GROUPS
.3-Methyl-l-buten-3-01 (6)
cn=c
1)
-OH CH2=CH CH3-CCX2)
CH3C F) CX1) COMPOSITION
Propargyl alcohol ( 4 )
CC 5)HClO)OC
FUNCTIONAL GROUPS
COCC)
CC 3)HC
1
COMPOSITION
COMPOSITION
4)0( 1)
CC 10)HC 1 6 ) O C 0)
FWNCTIONAL GROUPS
FUNCTIONAL GROUPS
-OH C(T)CH
CYCLOPROPANECZH) CH=C CH3-CCX2) CH3C F) CX1)
Figure 5. Reproduction of data computed by the master computer for trans-decaline (2), 3-methylcyclohexenone (3), propargy alcohol (4), 2-methylfuran (5),3-methyl-I-buten-3-01(6), and A*-carene(7)
COMPOS1TION
I
CC 5)HC 8 ) O C 1)
Dlhydzopyran (8)
FUNCTIONAL GROUPS CH=C -0-
-
300
240 C D
Figure 6. Reproduction of data computed by the master computer for dihydropyran (8), trans-crotonaldehyde (9), and camphene (10) Some of functional groups (under-
COMPOSITION CC 4 ) H C 6)OC
1)
FUNCTIONAL GROUPS CHOCC)
390 COMPOS1 TION C( 1 0 ) H ( 16)OC
Camphene (10)
CH=C cv=c CH3-CHCXB)
2222
0
ANALYTICAL CHEMISTRY
0)
FUNCTIONPL GROUPS
OR CH3-CCXB)
360 cps
lined) were miscomputed
eters and slave computers is fed into the master computer on which a program to elucidate the molecular formulas and partial structures of organic compounds is resident (Figure 2). The molecular formulas and partial structures are then printed out within several seconds. An example will be shown. First of all, four kinds of spectra for this sample were measured. The mass spectrum was converted into a tabulated form by the comparater and slave computer 1. The positions (cps), intensities, and areas for all signals of NMR spectrum of this sample were given by slave computer 2. Then the computer continued further calculations based on these data to find out the chemical shifts and coupling constants. IR spectrum was expressed in numerals by slave computer 3. Slave computer 4 also detected an absorption maximum at 220 mp (Figure 3). The master computer treated all the information to calculate the partial structures along the program already shown in Figure 2. In Figure 4, the first line stands for the molecular formula of this compound. CO(C) means this compound contains a conjugated carbonyl group. As another functional group, a trisubstituted olefin (CH=C) is present. Concerning methyl groups, the master computer suggests the presence of two possibilities, namely, three olefinic methyls [CHa(F)] or an acetyl and two olefinic methyls. Although the latter is actually correct, our program was not able to distinguish between these two possibilities. However, from these partial structures it will not be difficult to build the molecular structure of mesityl oxide (1) as one of the most reasonable structures for the examined compound. The printed out molecular formulas and functional groups of other samples are shown in Figure 5. For trans-decaline (2) only the molecular formula was given. For 3-methylcyclohexenone (3) the molecular formula and the presence of a carbonyl group with conjugation, a trisubstituted olefin, and an olefinic methyl were computed. For propargyl alcohol (4) a triple bond [C(T)CH] and a hydroxyl were suggested. For 2-methylfuran ( 5 ) a 2-substituted furan ring [furan(2)] and an olefinic methyl were suggested. Per 3-methyl-1-buten-
3-01 (6) a hydroxyl, a monosubstituted olefin (CHFCH) and two methyls at tertiary carbon (CHaC) were suggested. Finally for A*a-carene(7)a cyclopropane ring with two hydrogens [cyclopropane(2H)], a trisubstituted olefin, two methyls at tertiary carbon, and an olefinic methyl were provided. However, the nature of olefinic linkage of dihydropyran (8), trans-crotonaldehyde (9), and camphene (10) was miscomputed as shown in Figure 6. These inconsistencies are chiefly caused by the miscalculation of NMR spectra. In dihydropyran (8), CH=CH could not be observed because of a long ranged coupling of a proton at C-3. The transolefinic linkage of trans-crotonaldehyde (9) was not detectable because the J value of trans-protons is exactly two times the value of that between the methyl and the proton at C-3. Finally, the reason that two trisubstituted olefins were detected instead of terminal methylene in camphene (10) was that a pair of signals of the olefinic protons showed no coupling.
SHIN-ICHI SASAKI~ Miyagi University of Education Aoba, Sendai, Japan
HIDETSUGW Am Department of Chemistry Tohoku University Katahira, Sendai, Japan
TATSUMI OUKK MASAYOSHI SAKAMOTO SHUKICHI OCHIAE Japan Electron Optics Laboratory Akishima, Tokyo, Japan To whom communications should be addressed.
RECEIVED for review May 27,1968. Accepted August 5,1968. Presented at the Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Cleveland, Ohio, March 1968.
VOL. 40, NO. 14, DECEMBER 1968
e
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