Deuterium bromide chloride

The addition of hydrogen chloride and hydrogen bromide to norbornene is an interesting case, since such factors as facile rearrangement via a norbornyl cation and steric preference for attack from the exo side of the olefin come into consideration. Addition of deuterium bromide to norbornene gives exo-norbornyl bromide. Degradation to locate the deuterium atom shows that about half the product has been... 

There are three methods which are commonly used in the steroid field to replace a halogen atom by deuterium. These methods involve treatment of the halides— generally chloride, bromide or iodide—(a) with lithium aluminum deuteride, (b) with deuterium gas and a surface catalyst or (c) with zinc in O-deuterated acids or alcohols. 

Spectroscopic Analysis. Infrared (IR) spectroscopic analysis was performed on a Beckman Microlab 620 MX computing spectrometer. Samples were cast on a sodium chloride pellet or made into a pellet with potassium bromide. and 13C NMR spectra were obtained using a JEOL HNM-FX 270 MHz Fourier transform NMR spectrometer. Samples were dissolved in deuterium chloroform and chemical shifts were referenced to an internal standard of tetramethylsilane. 

Fig. 2 The temperature dependence of the vibrational contributions to the secondary a-deuterium KIE for the SN2 reaction between chloride ion and methyl bromide by (a) the high energy C —H(D) stretching vibrations, (b) the Ca—H(D) bending vibrations and (c) the low-energy transition state vibrations. Modified, with permission, from Hu...

A full report has now appeared of solvent effects on the rates of hydrolysis of benzyltriphenylphosphonium bromide. The remarkable increase in rate in media of low polarity is largely attributable to a shift of the pre-equilibrium between phos-phonium and hydroxide ions in favour of the intermediate hydroxyphosphorane.129 In a similar vein, a study of medium and deuterium isotope effects on the rate of hydrolysis of tetraphenylphosphonium chloride in acetone-water mixtures has been reported.130... 

Benzylic halides are reduced very easily using complex hydrides. In a-chloroethylbenzene lithium aluminium deuteride replaced the benzylic chlorine by deuterium with inversion of configuration (optical purity 79%) [537]. Borane replaced chlorine and bromine in chloro- and bromodiphenylme-thane, chlorine in chlorotriphenylmethane and bromine in benzyl bromide by hydrogen in 90-96% yields. Benzyl chloride, however, was not reduced [5iSj. Benzylic chlorine and bromine in a jy/n-triazine derivative were hydrogeno-lyzed by sodium iodide in acetic acid in 55% and 89% yields, respectively [5i9]. 

The halide sequence is completely reversed chloride ion > bromide ion > iodide ion. This has caused us some problem, but as yet we have no explanation for it. In both cases there is enough evidence from other kinetic investigations and deuterium labelling to realize that the metal with the attached organic group R... 

An intermolecular isotope effect, /h//d °f 200 has been reported [741, 742] for dissociative electron attachment of H2 and D2. The intermolecular deuterium isotope effects on dissociative electron attachment in hydrogen chloride, hydrogen bromide and hydrogen iodide have been determined as 1.41,1.45 and 1.66, respectively [168]... 

Presumably less nucleophilically assisted solvolyses could show higher a-deuterium isotope effects, and there is a linear relationship between the magnitude of nucleophilic solvent assistance (Table 2) and the a-deuterium isotope effect for solvolyses of 2-propyl sulpho-nates (Fig. 7). Another measure of nucleophilic assistance is the ratio k2 (OH )/, where k2 is the second-order rate constant for nucleophilic attack by OH and kx is the first-order rate constant for reaction with the solvent water, and a linear correlation was obtained by plotting the ratio versus the experimentally observed isotope effects for methyl and trideuteriomethyl sulphonates, chlorides, bromides and iodides (Hartman and Robertson, 1960). Using fractionation factors the latter correlation may also be explained by a leaving group effect on initial state vibrational frequencies (Hartshorn and Shiner, 1972), but there seems to be no sound evidence to support the view that Sn2 reactions must give a-deuterium isotope effects of 1-06 or less. 

Bis(phenylselanyl)methyllithiums 429 (R = H) are stable till 0 °C and were initially trapped with deuterium oxide, methyl iodide and benzophenone639. a-Substituted organolithium intermediate 429 (R = Me, w-CgH ), prepared with LiTMP in THF/HMPA at — 20 °C, reacted with alkyl bromides, ethylene oxide and benzaldehyde to give products 430 in good yields (Scheme 113)640. Bis(methylselanyl)methyllithiums 431 have been allowed to react with different electrophiles to afford products 432 (Scheme 113)640. Alkylated products have been deprotected with mercury(II) chloride or copper(II) chloride/copper(II) oxide, and by oxidation with hydrogen peroxide or benzeneseleninic anhydride644. Deprotection of selenoacetals to ketones can also be performed with sulfuric acid645. 

As shown in Section 25A, the components of infrared instruments differ considerably in detail from those in ultraviolet and visible instruments. Thus, infrared sources are heated solids rather than deuterium or tungsten lamps, infrared gratings are much coarser than those required for ultraviolet/visible radiation, and infrared detectors respond to heat rather than photons. In addition, the optical components of infrared instruments are constructed from polished solids, such as sodium chloride or potassium bromide. 

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