Problem 1
Draw the structures of (a) pentan-l-ol; (b) heptan- \(3-01\); (c) 2 -methylpentan-2-ol; (d) propane- 1,2,3 -triol.
Problem 6
Suggest starting materials for the preparation of the following alcohols using a Grignard reagent as one precursor. In each case, state how you might make the Grignard reagent: (a) 2 -methylpropan- 2 \(\mathrm{ol}\) (b) heptan-I-ol; (c) pentan-2-ol.
Problem 9
Suggest reasons for the following trend in \(\mathrm{p} K_{\mathrm{a}}\) values: EtOH, p \(K_{\mathrm{a}}=16.0 ; \mathrm{Me}_{3} \mathrm{COH}, \mathrm{p} K_{\mathrm{a}}=18.0\) \\[ \mathrm{CF}_{3} \mathrm{CH}_{2} \mathrm{OH}, \mathrm{p} K_{\mathrm{a}}=12.4 ;\left(\mathrm{CF}_{3}\right)_{3} \mathrm{COH}, \mathrm{p} K_{\mathrm{a}}=5.4 \\]
Problem 10
An alcohol \(\mathbf{X}\) has a composition of \(64.8 \% \mathrm{C}\) and \(13.6 \%\) H. The mass spectrum shows a parent ion at \(m / z=74 .\) The \(^{1} \mathrm{H}\) NMR spectrum of \(\mathbf{X}\) dissolved in \(\mathrm{CDCl}_{3}\) has signals at \(\delta 3.71\) (sextet, \(1 \mathrm{H}\) ), 2.37 (singlet, \(1 \mathrm{H}\) ), 1.46 (multiplet, \(2 \mathrm{H}\) ), 1.17 (doublet, 3H), 0.93 (triplet, \(3 \mathrm{H}\) ) ppm; in the \(^{13} \mathrm{C}\) NMR spectrum, four resonances are observed. Use these data to suggest a structure of \(\mathbf{X}\) and comment on isomer possibilities that retain the \(\mathrm{OH}\) functionality.
Problem 11
What spectroscopic technique(s) would you choose to distinguish between (a) propan-1-ol and propan-2-ol; (b) diethyl ether and butan-1-ol; (c) cyclohexanol and hexan-1-ol?
Problem 12
Sodium wire can be used to dry hexane solvent. (a) Write an equation for the reaction that occurs. (b) How might you destroy excess Na and what precautions should you take?
Problem 14
Suggest the identities of the major products in the acid-catalysed dehydrations of (a) butan-2-ol, (b) 2methylbutan-1-ol, (c) pentan-I-ol.
Problem 17
When we discussed oxidation of alcohols in Section \(30.5,\) we stated that the mechanism of oxidation of an aldehyde to carboxylic acid is analogous to that of the conversion of an alcohol to an aldehyde. Propose a mechanism for the oxidation of \(\mathrm{RCHO}\) to \(\mathrm{RCO}_{2} \mathrm{H}\) using \(\mathrm{KMnO}_{4}\) in acidic aqueous solution.
Problem 19
Suggest explanations for the following. (a) The \(^{1} \mathrm{H}\) NMR spectrum of \(\mathrm{CF}_{3} \mathrm{CH}_{2} \mathrm{OH}\) contains a quartet \((J 9 \mathrm{Hz})\) at \(\delta+3.9 \mathrm{ppm}\) in addition to the signal assigned to the OH proton. (b) The addition of \(\mathrm{D}_{2} \mathrm{O}\left(\mathrm{D}=^{2} \mathrm{H}\right)\) to hexanol causes the disappearance of the signal assigned to the OH proton. (c) Whereas alcohols exhibit relatively high boiling points and enthalpies of vaporization, the same is not true of thiols, \(\mathrm{RSH}\), e.g. propan-1-ol, bp \(=370.2 \mathrm{K}\) \(\Delta_{\mathrm{vap}} H(\mathrm{bp})=41.4 \mathrm{kJ} \mathrm{mol}^{-1} ;\) propane-l-thiol \(\mathrm{bp}=340.8 \mathrm{K}, \Delta_{\mathrm{vap}} H(\mathrm{bp})=29.5 \mathrm{kJ} \mathrm{mol}^{-1}\)
Problem 20
(a) Explain why the displacement of \(\mathrm{OH}\) in an alcohol by Br is carried out under acidic conditions. (b) Suggest products at each stage in the following reaction scheme: Why does the OH group need to be protected before the following reaction is carried out? (c) Suggest how you would prepare the following \(^{13}\) C-labelled compound \(\left(\boldsymbol{\theta}=^{13} \mathbf{C}\right)\) starting from the precursor shown below:
