Vinyl chlorides hydrogenolysis

During hydrogenation of vinylic chlorides, both saturation of the double bond and hydrogenolysis of the C-Cl bond take place.433 35 Also, selective hydrogenolysis of chlorine occurs in the presence of fluorine atoms on a Pd/C catalyst (Scheme 4.125).436... 

Like vinyl fluorides, vinyl chlorides suffer hydrogenolysis during catalytic hydrogenation. Rhodium is claimed to effect addition of hydrogen rather than hydrogenolysis of vinylic chlorides. However, hy-... 

A very active elemental rhodium is obtained by reduction of rhodium chloride with sodium borohydride [27]. Supported rhodium catalysts, usually 5% on carbon or alumina, are especially suited for hydrogenation of aromatic systems [iTj. A mixture of rhodium oxide and platinum oxide was also used for this purpose and proved better than platinum oxide alone [i5, 39]. Unsaturated halides containing vinylic halogens are reduced at the double bond without hydrogenolysis of the halogen [40]. 

In the absence of potassium hydroxide hydrogenation of vinylic and allylic chlorides to the saturated chlorides (with only partial or no hydrogenolysis of chlorine) is accomplished over 5% platinum, 5% palladium and, best of all, 5% rhodium on alumina [40]. 

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