3.3- Dimethyl-l-butanol

METHYL-1-BUTANOL 2-METHYL-2-BUTANOL 2 2-DIMETHYL-l-PROPANOL ETHYL PROPYL ETHER METHYL-T-BUTYL ETHER BUTYLMETHYL ETHER... 

DIMETHYL-l-PROPANOL tert-PENTYL-ALCOHOL 2-METHYL-1-BUTANOL... 

Problem 13.12. Give the product obtained when each of the following is heated in the presence of a strong acid (a) 1-butanol, (b) cyclohexanol, (c) 2,2-dimethyl-l-propanol. 

U.S. production of w-butanol has increased to 600 kt per annum, largely for conversion to unsaturated esters and saturated ester and ether solvents, while 2-ethylhexanol (about 300 kt per annum in the U.S., but much higher in Europe with exports at 250 kt per annum) is used mainly for the phthalate ester as a plasticizer for PVC. The n- and iso-butyraldehydes are also subjected to aldol condensation/crossed Cannizzaro reactions with formaldehyde, to give the polyols trimethylol-propane (2, 2-bishydroxymethyl-l-butanol) and neopentyl glycol (2,2-dimethyl-1,3-propanediol). 

The low Sn2 reactivity of 1°-alkyl bromide, 2,2-dimethyl-1-bromopropane (neopentyl bromide, 2.5), is explained by steric hindrance to the required 180° alignment of reacting orbitals. However, under Sn 1 conditions, neopentyl bromide (2.5) reacts at roughly the same rate as other 1°-alkyl halides such as ethyl bromide. Ionization of alkyl halides to carbocation in SnI is the rate-determining step. Although the product from ethyl bromide is ethanol as expected, neopentyl bromide (2.5) yields 2-methyl-2-butanol (2.6) instead of the expected 2,2-dimethyl-1-propanol (neopentyl alcohol) (2.7). This is because once formed the ethyl carbocation can only be transformed by a substitution or elimination process. In the case of the neopentyl carbocation, however, the initially formed l°-carbocation may be converted... 

The higher alcohol mixture has been found to contain the following primary alcohols ra-propanol, isobutanol, 2-methyl-l-butanol, 2-methyl-1-pentanol, 2,4-dimethyl-l-pentanol, 4-methyl-l-hexanol and the following secondary alcohols isopropanol, 3-methyl-2-butanol, and 2,4-dimethyl-3-pentanol. In addition, there are definite indications of 2,4-dimethyl-1-hexanol, 4 or 5-methyl-l-heptanol, 3-pentanol, 2-pentanol, and 2-methyl-3-pOntanol. ... 

Under conditions of kinetic control, the dehydration of 2-butanol follows the Saytzeff rule, but a greater yield of m-2-butene than trans-l-batenc is obtained. These observations have no parallel in acid- or base-catalysed or pyrolytic eliminations. However, the dehydration of 2,3-dimethyl-2-butanol gives 2,3-dimethyl-l-butene (88.4%) and 2,3-dimethyl-2-butene (9.9%) and is thus oriented towards the Hofmann rule despite being more probably a carbonium ion process. Under similar reaction conditions the quite distinctly different products arising from the secondary alcohol, 3,3-dimethyl-2-butanol [3,3-dimethyl-1-butene (70%), 2,3-dimethyl-l-butene (23.5%), 2,3-dimethyl-2-butene (3.9%), l,l-dimethyI-2-methylcyclopropane (2.1%)] are accommodated in terms of concerted rather than a carbonium-ion mechanism. 

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