Hydrogen iodide reaction with alcohols

This explanation indicates that the action of sodium upon alcohol is really the action of sodium upon water, partially olefinated. The action of ethyl iodide upon sodium ethoxide is not the replacement of the sodium by ethyl so much as the action of olefinated hydrogen iodide upon olefinated sodium hydroxide. It is the same type of reaction as the neutralization of sodium hydroxide by hydriodic acid in aqueous solution. The hydrated hydrogen iodide reacts with hydrated sodium hydroxide. The water bears the same relation to the latter reaction that the olefin does to the former. 

Another method for the hydrogenoiysis of aryl bromides and iodides is to use MeONa[696], The removal of chlorine and bromine from benzene rings is possible with MeOH under basic conditions by use of dippp as a ligand[697]. The reduction is explained by the formation of the phenylpalladium methoxide 812, which undergoes elimination of /i-hydrogen to form benzene, and MeOH is oxidized to formaldehyde. Based on this mechanistic consideration, reaction of alcohols with aryl halides has another application. For example, cyclohex-anol (813) is oxidized smoothly to cyclohexanone with bromobenzene under basic conditions[698]. 

The order of reactivity of the hydrogen halides parallels their acidity HI > HBr > HCl >> HF Hydrogen iodide is used infrequently however and the reaction of alco hols with hydrogen fluoride is not a useful method for the preparation of alkyl fluorides Among the various classes of alcohols tertiary alcohols are observed to be the most reactive and primary alcohols the least reactive... 

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 first reaction proceeds most easily with hydrogen iodide since in many cases mere saturation with the gaseous acid suffices to bring it about. Hydrogen bromide reacts with greater difficulty, and in its case it is frequently necessary to heat the alcohol saturated with this acid in a sealed tube. The preparation of ethyl bromide described above, in which the HBr is liberated from the potassium bromide by means of concentrated sulphuric acid, constitutes a very smooth example of this reaction. 

The nitrophenyl radical can react with the iodide ion and solvent, methanol, as well. Transference of hydrogen radical from methyl alcohol to nitrophenyl radical gives rise to nitrobenzene and formaldehyde (CHjOH —> CH2O). Though carefully sought among the products of the reaction, 3-iodonitro-benzene and 4-nitroanisole were lacking. This completely rejects another possible mechanism of the reaction, cine-substitution, which involves the formation of dehydrobenzene as described earlier. 

Phenylethyl Iodide. Use 146 g. (142 ml.) of (J-phenylethyl alcohol (b.p. 216 5-217°), 16 54 g. of purified red phosphorus and 154 g. of iodine. Lag the arm C (Fig.///, 40, 1) with asbestos cloth. Heat the alcohol - phosphorus mixture to boiling until sufficient alcohol (usually one-third to one-half of the total volume) passes into the reservoir B to dissolve all the iodine. Remove the flame and add the iodine solution at such a rate that the mixture boils gently. A little hydrogen iodide is evolved towards the end of the reaction. Allow the mixture to cool, add water and filter off the excess of phosphorus. Decolourise the filtrate with a little sodium bisulphite and add ether to assist in the separation of the water layer. Wash the ethereal solution with water, dry with anhydrous potassium carbonate, and distil under diminished pressure. B.p. 114 116°/12 mm. Yield 215 g. 

---