Hydroquinones, etherification

Clay-supported heteropoly acids such as H3PW12O40 are more active and selective heterogeneous catalysts for the synthesis of MTBE from methanol and tert-butanol, etherification of phenethyl alcohols with alkanols, and alkylation of hydroquinone with MTBE and tert-butanoi (Yadav and Kirthivasan, 1995 Yadav and Bokade, 1996 Yadav and Doshi, 2000), and synthesis of bisphenol-A (Yadav and Kirthivasan, 1997). 

Hydroquinone dimethyl ether is prepared by etherification of hydroquinone and is used in soap perfumes. 

The activity of the 2-alkylhydroquinones (la), 2,5-dialkyl-hydroquinones (lb), 2,6-dialkylhydroquinones (Ila), and of 2,5- and 2,6-dialkyl-4-alkoxyphenols (Ic and lib) was studied in isotactic polypropylene at 180 0.1° C. The values obtained were correlated with hydroquinone (Ari) and pyro-catechol (AT2). All compounds studied (la) except the tert-octyl derivative were inferior in activity to hydroquinone. Two alkyls of Types lb and Ha exerted further but nonadditive unfavorable effects, particularly the lb type. Despite over-all low values of Ari, a weak favorable steric effect of the tert-alkyls is apparent in Type la compounds. Etherification even as acetylation of one hydroxyl group (Ic, lib), has a strong favorable effect. These compounds were the most active antioxidants of the entire hydroquinone series studied nevertheless their activity did not reach that of pyrocatechol (At2 < 1). 

The direct coupling of monofiinctional polymers prepared by ATRP can also be realized by etherification reaction with low-molar mass dialcohols. Typically, the preparation of aldehyde functional a,co-telechelic polymers by classic etherification is demonstrated on the example hydroquinone as the coupling agent (Scheme 2). 

Nitrite (N02 ) catalyses mono-etherification of 1,4-hydroquinone (147) by methanol, via oxidation to the semi-quinone intermediate. " The reaction has been extended to other alcohols, and for substituted hydroquinones, reaction occurs exclusively at the less hindered phenol. 

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