Carboxyl groups, protection alcohols

Oxidation of LLDPE starts at temperatures above 150°C. This reaction produces hydroxyl and carboxyl groups in polymer molecules as well as low molecular weight compounds such as water, aldehydes, ketones, and alcohols. Oxidation reactions can occur during LLDPE pelletization and processing to protect molten resins from oxygen attack during these operations, antioxidants (radical inhibitors) must be used. These antioxidants (qv) are added to LLDPE resins in concentrations of 0.1—0.5 wt %, and maybe naphthyl amines or phenylenediamines, substituted phenols, quinones, and alkyl phosphites (4), although inhibitors based on hindered phenols are preferred. 

Photolytic cleavage reactions (e.g., of o-nitrobenzyl, phenacyl, nitrophenylsul-fenyl derivatives) take place in high yield on irradiation of the protected compound for a few hours at 254-350 nm. For example, the o-nitrobenzyl group, used to protect alcohols, amines, and carboxylic acids,has been removed by irradiation. Protective groups that have been removed by photolysis are described at the appropriate places in this book in addition, the reader may wish to consult five review articles. 

The dibenzosuberyl ether is prepared from an alcohol and the suberyl chloride in the presence of triethylamine (CH2CI2, 20°, 3 h, 75% yield). It is cleaved by acidic hydrolysis (1 N HCl/dioxane, 20°, 6 h, 80% yield). This group has also been used to protect amines, thiols, and carboxylic acids. The alcohol derivative can be cleaved in the presence of a dibenzosuberylamine. ... 

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