Deuteriated compounds

Dietary /1-carotene, a nutritionally important source of vitamin A, exhibits a protective effect against cancer risk31,32. The deuteriated compound, 10,10, 19,19,19,19, 19, 19 -2H8-/S-carotene, 32, has been obtained33 by double condensation of the C-15 Wittig salt 33 with the symmetrical C10 dial 2,7-dimethyl-2,4,6-octatrienedial, 34 (equation 13) for the study of /J-carotene metabolism in humans. 

Alkyl and Related Compounds. The i.r. spectra of MeTiClj and Me2TiCl2 and their deuteriated analogues have been redetermined the results do not agree with those obtained in earlier studies, and it would appear that authenticated samples of deuteriated compounds must be obtained before these discrepancies... 

The principal fragmentations experienced by 1,3-diphenylisoindole (for which the base peak corresponds to the molecular ion at m/e 269) yield peaks at m/e 267, 190 and 165. Proposed fragmentation pathways, elucidated with the aid of studies on the N-deuteriated compound, are shown in Figure 20. The mass spectrum of the related diphenylisoindoline, for which the base peak corresponds to loss of C6Hs and the next strongest peak loss of H, is described in the same paper (760MS258). Data for isoindole itself have been reported m/e 118 CM+, 26), 117 (100), 90 (74), 89 (56) and 63 (38) (73JCS(Pl)1432>. 

The Clemmensen reduction was accompanied by D/H exchange via acid-catalysed enolization of the carbonyl group, resulting in the production of deuteriated compounds 57 and 58 with various numbers of deuterium atoms. The mixture of the compound 59 obtained by the Wolf-Kishner reduction was predominantly labelled at position 2. This has been proved by the 13C-NMR spectrum. Isotope shift and loss intensivity on substituted C(2) carbon signals have been observed54,55. 

The intermediate bicyclo[2,2,l]heptyl cation has been written in Fig. 1 in its unbridged form by analogy with conclusions reached from studies of the Bamford-Stevens reaction of 18 stereospecifically deuteriated in either the 6-exo- or 6-endo positions (Nickon and Werstiuk, 1966). Under aprotic conditions (diglyme/sodium methoxide), the product is entirely norticyclene (19), formed without loss of deuterium in keeping with carbene formation followed by intramolecular insertion. Under standard protic conditions, 19 still constitutes more than 90% of the reaction product, but 19% of the label is lost from ea o-deuteriated starting material and 52% from the endo-deuteriated compound,... 

Figures 1.9a and b demonstrate the effect of proton broadband decoupling in the 13C NMR spectrum of a mixture of ethanol and hexadeuterioethanol. The CH3 and CH2 signals of ethanol appear as intense singlets upon proton broadband decoupling while the CD3 and CD2 resonances of the deuteriated compound still display their septet and quintet fine structure deuterium nuclei are not affected by lH decoupling because their Larmor frequencies are far removed from those of protons further, the nuclear spin quantum number of deuterium is ID = 1 in keeping with the general multiplicity rule (2 nxh+ 1, Section 1.4), triplets, quintets and septets are observed for CD, CD2 and CD3 groups, respectively. The relative intensities in these multiplets do not follow Pascal s triangle (1 1 1 triplet for CD 1 3 4 3 1 quintet for CD2 1 3 6 7 6 3 1 septet for CD3).

Answer 13.6 Since the hydride groups are labile, isolating the deuteriated compound by exchange under a D2 atmosphere in solution should be straightforward. 

In an earlier report Mazzocchi and his coworkers reported that the photo-reaction of A) methylnaphthalimide (325) with phenyIcyclopropane involved the production of a radical cation/radical anion pair. The product from the reaction was the cyclic ether (326). - A study of the mechanism of this reaction using suitably deuteriated compounds has demonstrated that the reaction is not concerted and takes place via the biradical (327). - Other systems related to these have been studied. In the present paper the photoreactivity of the naphthalimide (328) with alkenes in methanol was examined. Thus, with 1-methylstyrene cycloaddition occurs to the naphthalene moiety to afford the adducts (329) and (330). The mechanism proposed for the addition involves an electron transfer process whereby the radical cation of the styrene is trapped by methanol as the radical (331). This adds to the radical anion (332) ultimately to afford the observed products. Several examples of the reaction were descr ibed. 

An example of a reaction showing a primary deuterium isotope effect is reaction (2.40), in which acetone (propanone) reacts with bromine in the presence of base to give bromoacetone (bromopropanone). Under similar conditions, the fully deuteriated compound CD3COCD3 reacts about seven times more slowly. This is consistent with the mechanism shown the rate-determining step is the production of the anion 14 in the first step. The C-H bond is partially broken in the transition state, so the deuteriated compound will react more slowly. 

Q Propan-2-ol, Me2CHOH, is oxidized to acetone (propanone) by chromium(VI) in dilute add solution by the HCr04 anion at a rate proportional to [Me2CH0H](HCr04 ][H+ ]. The rate of reaction is reduced by a factor of about 7 if the deuteriated compound Me2CDOH is used instead. Which of the following mechanisms is consistent with this evidence ... 

The main uses of deuterium are in tracer studies to follow reaction paths and in kinetic studies to determine isotope effects. " A good discussion with appropriate references is in Comprehensive Inorganic Chemistry, Vol. 1, pp. 99-116. The use of deuterated solvents is widespread in proton nmr studies to avoid interference from solvent hydrogen atoms, and deuteriated compounds are also valuable in structural studies involving neutron diffraction techniques. 

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