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Organic Chemistry · Part 4 of 4
12 exam-style questions with model answers, plus 16 quick multi-choice questions — every question on this part of the standard, grouped by the 4 pages of notes they come from.
Write a full answer before you reveal the model one. That comparison is where the learning happens.
Write equations for the hydrolysis of methyl propanoate, CH3CH2COOCH3, with (a) dilute sulfuric acid and (b) aqueous sodium hydroxide, and name the organic products.
Explain why the base hydrolysis of an ester goes to completion but the acid hydrolysis does not.
A student refluxes an unknown compound of formula C5H11NO with aqueous sodium hydroxide and observes a gas that turns damp red litmus blue. On acidifying the remaining solution, a compound is obtained that fizzes with sodium carbonate and has the formula C4H8O2. Deduce the structure of the unknown, justify each step, and explain what a repeat of the experiment using dilute hydrochloric acid instead would have produced.
Name the type of link formed in a polyester and in a polyamide, state the small molecule lost when a dicarboxylic acid reacts with a diol, and name this type of polymerisation.
The amino acid alanine has the structure H2N–CH(CH3)–COOH. Draw a section of the protein chain formed from three alanine molecules, and explain why alanine can polymerise with itself while ethylamine cannot.
Kevlar is a polyamide made from benzene-1,4-dicarboxylic acid and benzene-1,4-diamine. Poly(ethene) is made from ethene. Compare and contrast the two polymerisations, and justify why Kevlar can be broken down by hot concentrated acid but poly(ethene) cannot.
Name the alcohol from which all triglycerides are formed, state how many ester links a triglyceride contains, and name the products of its hydrolysis with hot aqueous sodium hydroxide.
Explain why a triglyceride made from unsaturated fatty acids is usually a liquid at room temperature, while one made from saturated fatty acids of similar chain length is a solid.
Explain how soap removes grease from a fabric, relating your answer to the structure of the soap molecule produced by saponification. Justify why the acid hydrolysis of a triglyceride would not produce an effective soap.
Give a two-step route to convert 2-bromopropane into propanone, stating the reagents and conditions and the intermediate product.
Devise a route to convert propan-1-ol into propyl propanoate, using propan-1-ol as the only organic starting material. Explain why the starting material must be divided into two portions.
Three students propose routes from propan-1-ol to ethyl propanoate, with ethanol also available.
Student A: oxidise propan-1-ol to propanoic acid, then react with ethanol and conc. H2SO4. Student B: oxidise propan-1-ol to propanal, then react with ethanol and conc. H2SO4. Student C: oxidise propan-1-ol to propanoic acid, convert to propanoyl chloride with SOCl2, then react with ethanol.
Evaluate all three routes and justify which is best.