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16. Hydroxy compounds

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  1. 16.1 Alcohols

    1. 16.1.1Preparation of alcohols

      • Recall preparation of alcohols - (a) electrophilic addition of steam to an alkene, using H2O(g) and H3PO4 catalyst - (b) reaction of alkenes with cold dil. acidified potassium manganate( VII) to form a diol - (c) substitution of a halogenoalkane using NaOH(aq) and heat - (d) reduction of an aldehyde or ketone using NaBH4 or LiAl H4 - (e) reduction of a carboxylic acid using LiA l H4 - (f) hydrolysis of an ester using dil. acid or dil. alkali and heat

    2. 16.1.2Describe

      • Describe: - (a) the reaction with oxygen (combustion) - (b) substitution to form halogenoalkanes, e.g. by reaction with HX(g); or with KCl and concentrated - H2SO4 or conc. H3PO4; or with PCl 3 and heat; or with PCl5; or with SOCl 2 - (c) the reaction with Na(s) - (d) oxidation with acidified K2Cr2O7 or acidified KMnO4 to: - (i) carbonyl compounds by distillation - (ii) carboxylic acids by refluxing (primary alcohols give aldehydes which can be further oxidised to carboxylic acids, secondary alcohols give ketones, tertiary alcohols cannot be oxidised) - (e) dehydration to an alkene, by using a heated catalyst, e.g. Al2O3 or a conc. acid - (f) formation of esters by reaction with carboxylic acids and conc. H2SO4 as catalyst as exemplified by ethanol

    3. 16.1.3Classify alcohols as primary, secondary

      • One alcohol group: (a) classify alcohols as primary, secondary and tertiary alcohols, to include examples with more than; (b) state characteristic distinguishing reactions, e.g. mild oxidation with acidified K 2Cr2O7, colour change; from orange to green

    4. 16.1.4CH3CH(OH)- alcohol identification

      • Deduce the presence of a CH3CH(OH)– group in an alcohol, CH3CH(OH)–R, from its reaction with alkaline I2(aq) to form a yellow precipitate of tri-iodomethane and an ion, RCO2 –

    5. 16.1.5Acidity of alcohols compared with water

      • Explain the acidity of alcohols compared with water