Secondary deuteriated

Subsequent work confirmed this apparently abnormal behaviour. Deuteriation at remote sites (the S- or e-position) induces small inverse secondary isotope effects in a-cleavages occurring in the ion source, but normal isotope effects in the decomposition of metastable ions in the field-free regions94,95. The time dependence of the isotope effect was also studied by field ionization kinetics, which permit the analysis of fragmentations occurring after lifetimes as short as 10 12 s-1. It was found that the inverse isotope effect favouring loss of the deuteriated radical operates at times shorter than 10 9 s95. 

Various solvents have been used in 29Si NMR studies and applications. It appears that the choice of solvent and concentration has been dictated more by the tradition in the particular field of organosilicon chemistry or laboratory than by the more general consideration of obtaining comparable and reproducible results. The solvents used include chloroform, benzene, tetrahydrofuran, pyridine, dioxane, dimethyl sulfoxide etc., usually in their fully deuteriated isotopomers the effects of these solvents on common secondary references were summarized earlier in Table 2. 

Recently, Capon and Wu49 have reported the generation of secondary enamines from their TV-trimethylsilyl derivatives through hydrolysis. In DMSO-d6 (99% v/v)-D20 (1% v/v) solution, enamine 40 is converted to the TV-deuteriated enamine 41 quantitatively in 5-10 min at room temperature. The solution obtained is stable for several hours, but over a period of 2-3 days 41 is oxidized to acetone and iV-deuterio-TV-phenylforma-mide. On adding 15% (v/v) D20/DC1 (0.1 M) to the solution, enamine 41 is completely hydrolyzed to 2-[2//]isobutyraldehyde and aniline without detection of any intermediates. Enamine 42 is formed by the acid-catalyzed hydrolysis of 40 (Scheme 3). Similar results are obtained with other iV-aryl enamines. 

Deuterium labelling studies have also been used to investigate the reaction of stilbenes and related compounds with amines (Lewis, 1979). It is known that tertiary amines form fluorescent exciplexes with stilbenes in nonpolar solvents and that polar solvents are necessary for chemical reaction to occur (Lewis and Ho, 1977). This suggests that radical ions are involved in product formation. When secondary amines are used, reaction occurs in solvents of widely differing polarity and this is presumably due to the acidity of the secondary N—H bond. N-deuteriated diethylamine reacts with 1,2-diphenyl-cyclobutene in benzene to give products [65], [66] and [67] incorporating deuterium (Scheme 6). For the reaction with unsymmetrically substituted... 

With primary or secondary amides, reaction with LiAlH4 is wasteful in that hydrogen gas is evolved and reduction usually proceeds through to the amine. Nevertheless, it has been shown that r-butylamides, refluxed with an excess of LiAlD4 for 15 h in diethyl ether, give very good yields of deuteriated aldehydes, RCDO. O ... 

Furthermore, the magnitude of kn/kD is shown to reflect the tightness or distance dxY in Scheme 22. The kH/kD values measured in MeCN with deuteriated anilines are presented in Table 3 for secondary alkyl arenesulfonates52. For these reactions, the size... 

This may be illustrated by re-examining a reaction that we have already studied. Earlier, we saw that when a 1,2-dibromide was treated with iodine, the reaction followed a normal anti-E2 pathway to eliminate a bromine molecule, which meant that the threo isomer yielded the trans isomer. If this elimination reaction is performed when either, or both, of the bromine atoms is, or are, attached to a primary carbon (instead of a secondary or tertiary carbon as was the case when we first looked at this reaction), then a different stereochemistry results. When this experiment is performed with deuteriated derivatives, it becomes apparent that the threo isomer gives the cis isomer. Suggest an explanation for this result. 

Band Assignment and Structural Elucidation.—The change in frequency of v(PH) from 2410 to 1753 cm upon deuteriation confirmed the presence of a PH bond in (121). In contrast to v(OH) of acidic and alcoholic OH groups, v(PH) of the phosphonium salt (121) is at higher wavenumber than v(PH) for primary and secondary phosphines ca. 2300 cm" ), and it is still... 

The lack of a large intramolecular deuterium isotope effect in the reaction of hot tritium with partially deuteriated methanes has been explained by Rowland and coworkers by postulating the existence of a very large secondary deuterium isotope effect which counterbalances the normal primary replacement isotope effect. 

The acid-induced reaction of aryldiazomethanes with olefins gives arylcyclo-propanes in addition to olefins and esters. The cyclopropanes are formed stereo-specifically and their yields are largest in reactions with olefins which on cation addition give secondary carbonium ion centres. The use of deuteriated acids leads to partial incorporation of deuterium in the cyclopropane adducts, whereas the use of [a- H]-phenyldiazomethane leads to partial loss of deuterium, suggesting a slow proton transfer from the acid to the diazo-compound a carbenoid rather than a free carbene appears to be involved. 

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