Chapter 29, Ethers Video Solutions, Chemistry

02:43

Problem 1

Give names for the following ethers:

Shazia Naz

Numerade Educator

03:17

Problem 2

Draw the structures for the following compounds: (a) diethyl ether; (b) ethoxyethane; (c) ethoxyheptane; and (d) 4,7 -dioxadecane.

Shazia Naz

Numerade Educator

03:51

Problem 3

Draw the structures for the following compounds: (a) THF; (b) diglyme; (c) 1,4,7-trioxacyclononane; (d) furan; and (e) oxirane.

Shazia Naz

Numerade Educator

03:03

Problem 4

Draw structures for the following compounds: (a) epoxypropane; (b) methyloxirane; (c) trimethyloxirane; (d) 1,2 -epoxycyclohexane; (e) 3,4 -epoxyheptane; and (f) 2 -ethyl- 3,3 dimethyloxirane.

Dr. Satish Ingale

Numerade Educator

02:50

Problem 5

Why would it be inefficient to prepare ethyl methyl ether by a method analogous to that shown in equation $29.1 ?$ What reaction(s) could you use to prepare this ether?

Shazia Naz

Numerade Educator

03:50

Suggest products for the reactions of (a) chloroethane with ethoxide, (b) iodomethane with potassium tert-butoxide, (c) methoxide with 2-chloro-2-methylpropane and (d) iso-propoxide with iodomethane. Draw the structure of each product.

Shazia Naz

Numerade Educator

01:41

Problem 7

Give the products of the reactions between perbenzoic acid and (a) ( $Z$ )-but-2-ene and (b) $(E)$ -but- 2 -ene. Rationalize your answer.

Shazia Naz

Numerade Educator

02:59

Problem 8

(a) The text in Section 29.4 states that a 'cyclic ether possesses a higher dipole moment than its acyclic analogue'. With reference to the data in Table 29.3 suggest reasons for this observation. (b) Are the following molecules polar: 1,3-dioxalane; 1,4-dioxane; furan; dibutyl ether?

Shazia Naz

Numerade Educator

01:35

Problem 9

(a) To what do you assign the broad band near $3400 \mathrm{cm}^{-1}$ in the spectra of the ethers in Figure $29.4 ?$ (b) How might you distinguish diethyl ether and methyl propyl ether using routine techniques?

Shazia Naz

Numerade Educator

03:06

Problem 10

Comment on the following data. The $^{1}$ H NMR spectrum of diglyme contains a singlet at $\delta$ $3.38 \mathrm{ppm}$ and two multiplets at $\delta 3.58$ and $3.64 \mathrm{ppm} .$ In the $^{13} \mathrm{C}$ NMR spectrum, three signals are observed.

Dr. Satish Ingale

Numerade Educator

02:58

Problem 11

A cyclic ether, $\mathbf{A},$ shows a quintet $(\delta 2.72 \mathrm{ppm})$ and triplet $(\delta 4.73 \mathrm{ppm})$ with relative integrals of $1: 2 .$ The mass spectrum of A has a parent peak at $m / z=58 .$ (a) Suggest a possible structure for $\mathbf{A}$ (b) What would you expect to observe in the $^{13} \mathrm{C}\left\{^{1} \mathrm{H}\right\} \mathrm{NMR}$ spectrum of $\mathrm{A} ?$

Dr. Satish Ingale

Numerade Educator

04:40

Problem 12

What would you expect to be the outcome of (a) heating $\mathrm{Et}_{2} \mathrm{O}$ and $\mathrm{HBr} ;$ (b) heating $\mathrm{Et}_{2} \mathrm{O}$ with $\mathrm{HCl} ;(\mathrm{c})$ adding a little $\mathrm{Et}_{2} \mathrm{O}$ to water; (d) placing a few drops of $\mathrm{Et}_{2} \mathrm{O}$ on your hand? Comment on any hazards involved.

Shazia Naz

Numerade Educator

05:30

Problem 13

Compare scheme 29.18 with equation $26.30 .$ Comment (with reasoning) on similarities and differences between them.

Dr. Satish Ingale

Numerade Educator

04:56

Problem 14

Outline the mechanisms of the reactions of methyloxirane with (a) HBr and (b) EtO $^{-}$ in ethanol, and comment on the regioselectivity of the reactions.

Dr. Satish Ingale

Numerade Educator

01:16

Problem 15

Suggest products for the following reactions:

Shazia Naz

Numerade Educator

02:11

Problem 16

A compound X has strong or very strong absorptions in its IR spectrum at 2961,2930 2871 and $1110 \mathrm{cm}^{-1} .$ Elemental analysis shows that $\mathbf{X}$ contains $75.9 \%$ C, $14.0 \%$ H and $10.1 \%$ O. Reaction of X with HI at elevated temperature gives compounds $\mathbf{Y}$ and $\mathbf{Z}$ which analyse as containing: $\mathbf{Y}, 30.3 \%$ C, $5.6 \%$ H, $64.1 \%$ I, and $\mathbf{Z}$ $68.1 \% \mathrm{C}, 13.7 \% \mathrm{H}$ and $18.2 \%$ O. The parent ion of $\mathbf{Y}$ in its mass spectrum is at $m / z 198 .$ What can you deduce about the identities of $\mathbf{X}, \mathbf{Y}$ and $\mathbf{Z}$ and what other information would be useful in determining the exact structures of the compounds?

Shazia Naz

Numerade Educator

02:18

Problem 17

Organic sulfides are related to ethers by exchange of S for O. (a) Draw the structure of diethyl sulfide. (b) Suggest a method of preparing methyl iso-propyl sulfide. (c) $\mathrm{Me}_{2} \mathrm{S}$ reacts with MeI to give an ionic salt. Suggest a mechanism for the reaction and the structure of the product.

Shazia Naz

Numerade Educator

01:18

Problem 18

Guaifenesin (3-(2-methoxyphenoxy)propane-1,2diol) is an active ingredient in expectorants which are sold to relieve coughs. Currently (2008), guaifenesin is the only expectorant approved by the US Food and Drug Administration (FDA).
(a) Suggest a method by which you could prepare guaifenesin starting from 2 -methoxyphenol and a suitable derivative of propane-1,2-diol.
(b) Guaifenesin is chiral but is administered in cough mixtures as a racemate. How does the chirality arise? Draw the structures of the two enantiomers and assign $(R)$ and $(S)$ labels.
(c) The solubility of guaifenesin is $1 \mathrm{g}$ per $20 \mathrm{cm}^{3}$ of water at 298 K. The solubility in hot water is much higher. What properties of the molecule contribute towards it being soluble? Draw appropriate diagrams to illustrate the origin of the drug's solubility in water.

Shazia Naz

Numerade Educator

02:00

Problem 19

'Fuel oxygenates' are added to automobile fuels so that they burn efficiently, thereby reducing the levels of CO and hydrocarbon emissions. Fuel oxygenates were developed in the 1970 s to replace lead-based fuel additives, and are typically ethers (e.g. $\mathrm{MeO}^{\mathrm{t}} \mathrm{Bu}, \mathrm{EtO}^{\mathrm{t}} \mathrm{Bu}$ ) or alcohols (e.g. $\mathrm{EtOH}$
$^{t} \mathrm{BuOH}$. The most commonly employed additive is $\mathrm{MeO}^{t} \mathrm{Bu}$ (known as MTBE). However, its appearance in groundwater and drinking water is a cause for concern. (a) Draw the structure of MTBE. (b) MTBE is very mobile in groundwater. Suggest an explanation for this observation. (c) What do you think are the primary routes by which MTBE in fuel enters water supplies? (d) There are some calls for $\mathrm{EtO}^{1} \mathrm{Bu}$ or $\mathrm{EtOH}$ to replace MTBE as the major fuel additive. How would this help a directive such as that laid down by the European Union to increase the addition of biofuel to automobile fuels?

Shazia Naz

Numerade Educator

01:16

Problem 20

Sulfur analogues of peroxides (ROOR') are called disulfides (RSSR'). The tendency for sulfur to undergo catenation (i.e. form chains, see Section 9.8 ) means that compounds of type RSSSR' (trisulfides) are known but oxygen analogues are not. Thiosulfinates are volatile, sulfur-containing compounds present in members of the Allium family, most notably onion (Allium cepa) and garlic (Allium sativum), and give rise to the characteristic smell and taste of these plants. In garlic, allicin is the most important thiosulfinate: Thiosulfinates are unstable compounds and undergo a range of chemical transformations. Hence, the characteristic odours arising from garlic and onions arise from a mixture of volatile sulfur-containing compounds including those shown below: (a) Suggest why there is no oxygen analogue of allicin, i.e. with the two S atoms replaced by O atoms. (b) Mixtures of volatile compounds from a freshly cut piece of onion or garlic may be analysed by using GC-MS. Briefly outline what this method involves, and state how mass spectrometry aids the identification of the compounds shown above. What other techniques would be useful?

David Collins

Numerade Educator

04:38

Problem 21

The following compound is a sex pheromone of the female Japanese beetle (Popillia japonica). The structure drawn is that of the naturally occurring form. (a) Where is the stereogenic centre in this molecule? (b) Is the naturally occurring form the
$(R)$ or $(S)$ -enantiomer? (c) Draw the structures of the other possible isomers of this compound, and assign appropriate stereochemical labels.

Dr. Satish Ingale

Numerade Educator

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