ARE YOU MISSING THE INFORMATION THAT NMR SPECTROSCOPY CAN FURNISH?
55
Ν
(Nuclear Magnetic Resonance)
AT
- M - R W O R K
VARIAN'S UNIQUE APPLICATIONS LABORATORY CAN SUPPLY THESE MISSING DATA NMR Spectroscopy is α molecular study method that uses a different parameter than any other technique. It can often contribute where other methods are "blind" or inconclusive. Hence NMR may question, confirm or supplement the deductions from your present study methods. The nuclei H', H 2 , F", P31 and B" yield strong NMR signals that "describe" their molecular surroundings. Thus NMR aids in determining correct structural formulas of such substances as steroids, boranes, natural products and products of organic synthesis. It is useful in studies of molecular conformation, electron distribution in molecules, reaction kinetics, and potential energy barriers in molecules. For example, it determines position and extent of deuterium substitution in organic compounds for study of reaction mechanisms. Varian's High Resolution NMR Applications Laboratory has for some time been examining suitably qualified chemical samples on a complimentary exploratory basis. Now in addition Varian will accept a limited number of samples on a fee basis. For $25 Varian will furnish a brief interpretation and an NMR spectrum taken under standard conditions. More complex studies will sometimes be undertaken on an hourly fee basis.
5 5 of a series QUANTITATIVE
MEASUREMENT OF DEUTERIUM
INTERPRETATION: The determination of the position and extent of re placement by deuterium of hydrogen in a complex molecule is readily accomplished by High Resolution NMR spectroscopy. In the example below 1 , it is apparent that since only the peak corresponding to the proton H a (see trace A) has diminished in the deuterated sample (see trace B), the substitution has occurred entirely at that site. The com pleteness of the deuferation can be checked by two independent methods. The remaining H a signal in methoxychlor-d can be compared with the one from ordinary methoxychlor, correcting for the difference in receiver gain settings and differences in concentration of the two
samples. This gives 98.3% deuterium. One can also compare the area under peak H a in the methoxychlor-d spectrum with one of the two peaks due to C l ! H j O - in the same molecule (see trace C). This peak contains half the intensity from 1.1 percent of the molecules, or .55 percent of the C 1 H j O - peak, but since there are 6 methoxy protons, it corresponds to 3.3 percent hydrogen. The area of Ha is 0.65 that of C M H j O - , giving 97.8% deuterium. The average is 98.1 ± 0 . 3 % . Both compounds were studied as 40% solutions in ordinary acetone, whose resonance does not appear in this region of the spectrum. (1) The samples were furnished
through the kind cooperation
and D.J. Hennessy, Department
Write Mr. L. F. Johnson for lull information on Varions laboratory services. Current literature on Varian's NMR and EPR spectrometers will also be furnished, if requested. See us at the Pittsburgh Spectroscopy S h o w , M a r c h 2 to 6 , Booth 1 0 0 Circle No. 1 5 8 on Readers' Service Card 68 A
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ANALYTICAL CHEMISTRY
SUBSTITUTION
of Chemistry, Fordham
of Andrew C. Dachauer Univ.
VARIAN associates INSTRUMENT PALO
ALTO
4,
DIVΊSION C A L I F O R N I A
