Hydrogen iodide with alcohols

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... 

Alcohols react with nascent hydroiodic acid to form alkyl iodides. When the starting material is an alcohol ether sulfate, the resulting alcohol ethoxylate obtained by acid hydrolysis of the sulfate gives the corresponding alkyl iodides. The number of moles of diiodoethane equals the number of moles of ethylene oxide present in the alcohol ethoxylate. Diiodoethane decomposes or reacts with more hydrogen iodide to give iodine quantitatively in both cases. However,... 

N-Methylethylamine has been prepared by heating ethyl-amine with methyl iodide in alcohol at 100° 3 by the hydrolysis of N-methyl-N-ethylarenesulfonamides,4-5 -nitroso-N-methyl-N-ethylaniline,6 or methylethylbenzhydrylidene ammonium iodide 7 by catalytic hydrogenation of ethyl isocyanate or ethyl isocyanide 8 and by the reduction of ethyl isocyanate by lithium aluminum hydride,9 of N-methylacetisoaldoxime by sodium amalgam and acetic acid,10 or of a nitromethane/ethylmagnesium bromide adduct by zinc and hydrochloric acid.11... 

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. 

As esters the alkyl halides are hydrolysed by alkalis to alcohols and salts of halogen acids. They are converted by nascent hydrogen into hydrocarbons, by ammonia into amines, by alkoxides into ethers, by alkali hydrogen sulphides into mercaptans, by potassium cyanide into nitriles, and by sodium acetate into acetic esters. (Formulate these reactions.) The alkyl halides are practically insoluble in water but are, on the other hand, miscible with organic solvents. As a consequence of the great affinity of iodine for silver, the alkyl iodides are almost instantaneously decomposed by aqueous-alcoholic silver nitrate solution, and so yield silver iodide and alcohol. The important method of Ziesel for the quantitative determination of alkyl groups combined in the form of ethers, depends on this property (cf. p. 80). 

---