Hydrogen halogen reaction with

For reaction with hydrogen haUdes, the substitution reaction with haUde ion easily occurs when a cuprous or cupric compound is used as the catalyst (23) and yields a halogenated aHyl compound. With a cuprous compound as the catalyst at 18 °C, the reaction is completed in 6 h. Zinc chloride is also a good catalyst (24), but a by-product, diaHyl ether, is formed. 

Other Reactions. Primary amyl alcohols can be halogenated to the corresponding chlorides by reaction with hydrogen chloride in hexamethylphosphoramide (87). Neopentyl chloride [753-89-9] is formed without contamination by rearrangement products. A convenient method for preparing / f/-amyl bromide and iodide involves reaction of / f/-amyl alcohol with hydrobromic or hydroiodic acid in the presence of Li or Ca haUde (88). The metal haUdes increase the yields (85 —95%) and product purity. 

The reactions of halogens and hydrogen halides with alkenes are electrophilic addition reactions. This means that the initial attack on the organic molecule is by an electron-deficient species that accepts a lone pair of electrons to form a covalent bond. This species is called an electrophile. In the case of the reaction with hydrogen bromide, the mechanism for the reaction is as shown. 

RhX(CO)(PPh3)2 [X=halogen] complexes with hydrogen. The reaction for X=C1 is shown in Figure 11.3. 

Alkenes undergo addition reactions with hydrogen to form alkanes, with halogens to form dihaloalkanes, with hydrogen halides to form monohaloalkanes and with water to form alcohols. For example ... 

Reaction with hydrogen occurs at temperatures of 300 to 1,000°C forming a brittle dihydride, ZrH2. Zirconium combines with halogens at high temperatures forming tetrahalides. Reactions occur in the range 200 to 400°C. Sohd tetrahalides sublime above 300°C. 

The most effective synthesis for thietanones is the eliminative cyclization of halogenated ketones with hydrogen sulfide ions in the presence of bases (Eq. lOb). The reaction of 1,3-dibromoketone derivatives with sodium hydrogen sulfide produced 3-thietanones in association with a five-membered cyclic disulfide (Eq. 10c). 

Reaction with Hydrogen Halogens react with hydrogen gas to yield hydrogen halides, HX ... 

Tributyltin hydride (Bu3SnH) is used synthetically to reduce alkyl halides, replacing a halogen atom with hydrogen. Free-radical initiators promote this reaction, and free-radical inhibitors are known to slow it or stop it. Your job is to develop a mechanism, using the following reaction as the example. 

It undergoes addition reactions with hydrogen, halogens, hydrogen halides and water. 

Organotin halides can also be obtained from oxides or hydroxides on reaction with hydrogen halides (or ammonium halides) (equation 61) and from tin-tin bonded species on reaction with halogens (equation 62). 

The question also arises how far the comparison may be extended to reactions which are not ionic. In the first instance we can only say that reactions must at least exist which are related to the polar nature of the linkage, e.g. the hydrolysis of halogen compounds or esters, but not (as one might expect) the reduction of halogen compounds with hydrogen. 

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