Deoxymercuration

Abstract

The conversion of several stereoisomeric osymercurials to allcenes (deosymercuration) has been studied with hydrogen chloride in anhydrous and near-anhydrous methanol. In each instance the addition of water decreases the second-order rate. In benzene the addition of water to the anhydrous system first accelerates and then decreases the reaction rate. These results have been interpreted in support of molecular rather than ionic participation by hydrogen chloride. Since molecular participation requires the TT arrangement of alkoxy and chloromercuri groups for easy reaction it follows that oxymercuration also follows a molecular and not a "rnercurinium ion" mechanism in the normal reaction.The decomposition of 2-oxyorganomercuric salts to mercuric salts and alltenes has been called deoxymercuration (11). I t is a much milder reaction than is the scission of simple alkylmercuric salts, some of which resist prolo~lged heating with strong acids. This difference must be due to the vici~lal oxygen linltage. Several opinions have been expressed about the mallller in which this oxygen assists the scission of the carbon-mercury link. I t will be seen that these opi~lions are closely related to the ideas of oxymercurial formation. For this reason a decision about the manner in which deoxymercuration occurs ought to specify the mechanism of oxymercur a t' lon.According to Whitmore (20) deoxymercuration is induced by formation of an oxonium salt, I, which then decomposes into an alcohol, an alkene, and a mercuric rnonocation (where X is an acid substituent bound covalently).According to this mechanism the rate of deoxymercuration ought to be dependent on the strength of the acid used in the reaction. This dependence on acid strength has been confirmed by experiment (1 1).According to another, more recent, opi~lion the reaction is of the "E2 elimination" type (22) in which an anion is presumed to coordinate with the mercurial (11) to force the -8

Mechanisms of Elimination Reactions. XXI. The Alkaline Dehydrochlorination of meso- and dl-Stilbene Dichlorides1

“…Cram, Greene and DePuy6 have suggested that three canonical forms IX, X and XI, where B is base and SOH the solvent, may contribute to the transition state for bimolecular elimination. They have pointed out that only if X is the major contributing form {i.e., only if the transition state has considerable olefin character) will the groups (11) This may be due to one or several effects such as a slight impurity in the starting dichloride, the reaction of some of the base with the walls of the container, and the errors inherent in running a secondorder rate as if it were pseudo-first-order.…”

On the hot metal desulfurization

“…Although zirconium has a greater affinity for oxygen than aluminium, Zr in Fe-S alloys did not increase the rate of desulfurization. Figure 2 shows a large increase in the rate ence of a liquid phase at the interface gives rise to interfacial turbulence [8] as described in figure 4. The transfer of sulfur from the metal to the CaO disc surface causes a decrease in the interfacial tension and any local variation in the interfacial tension causes a disturbance in the form of a dilation.…”

Conformation and stereodynamics of N,N-dialkylbenzamides; a 1H and 13C nuclear magnetic resonance investigation of para-substituted 4-benzoyl-cis-2,6-dimethylmorpholines

“…The para-substituted 4-benzoyl-cis-2,6-dimethylmorpholines (1)--( 6) and (8) were prepared by dropwise addition of an equimolar mixture of commercial 2,6-dimethylmorpholine (containing ca. 70% of the cis-isomer) and anhydrous triethylamine to an equimolar proportion of the appropriate benzoyl chloride in anhydrous diethyl ether at 0°C.…”

“…In order to render this process observable by n.m.r. without resort to optically active additives, a series ofpara-substituted 4benzoyl-cis-2,6-dimethylmorpholines (1)- (8) were prepared for investigation. The presence of the chiral centres in these compounds ensures that the ortho-and meta-hydrogen and carbon atoms are diastereotopic even if the frozen ground-state conformation has the phenyl ring orthogonal to the amide plane or rapidly oscillating through this plane.…”