ChemistryCode 9701
Alcohols
What this topic asks you to be able to do
- recall the reagents and conditions for producing alcohols via: (a) electrophilic addition of steam to an alkene, with H2O(g) and an H3PO4 catalyst (b) cold dilute acidified potassium manganate(VII) acting on alkenes, forming a diol (c) substituting a halogenoalkane by heating it with NaOH(aq) (d) reducing an aldehyde or ketone with NaBH4 or LiAlH4 (e) reducing a carboxylic acid with LiAlH4 (f) hydrolysing an ester with dilute acid or dilute alkali and heat
- describe: (a) combustion, the reaction with oxygen (b) substitution to give halogenoalkanes, e.g. using HX(g); or KCl with concentrated H2SO4 or concentrated H3PO4; or PCl3 with heat; or PCl5; or SOCl2 (c) how an alcohol reacts with Na(s) (d) oxidising it with acidified K2Cr2O7 or acidified KMnO4 into: (i) carbonyl compounds, collected by distillation (ii) carboxylic acids, obtained by heating under reflux (a primary alcohol forms an aldehyde that can be oxidised further to a carboxylic acid; a secondary alcohol forms a ketone; a tertiary alcohol cannot be oxidised) (e) dehydration to an alkene over a heated catalyst, e.g. Al2O3, or with a concentrated acid (f) making esters by reacting the alcohol with carboxylic acids, with concentrated H2SO4 as catalyst, as shown by ethanol
- classify alcohols as primary, secondary or tertiary, including examples that carry more than one alcohol group (b) state the reactions, typical of each type, that tell them apart, e.g. mild oxidation with acidified K2Cr2O7, where the colour turns from orange to green
- deduce that an alcohol contains a CH3CH(OH)– group, written as CH3CH(OH)–R, from its reaction with alkaline I2(aq) producing a yellow precipitate of tri-iodomethane alongside an RCO2– ion
- account for the acidity of alcohols when set against water