Four esters, $$$\mathbf{A}, \mathbf{B}, \boldsymbol{C}$$$ and $$$\mathbf{D}$$$, with the molecular formula $$$\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{2}$$$ are shown in Fig. 7.1. Separate samples of the esters, A, B, C and D, are analysed using proton ( $$$\left.{ }^{1} \mathrm{H}\right)$$$ NMR and carbon-13 NMR spectroscopy. (i) Complete Table 7.1 to show the number of peaks in each NMR spectrum for esters B and $$$\mathbf{C}$$$. (ii) Identify all of the esters from A, B, C and D that have at least one triplet peak in their proton $$$\left({ }^{1} \mathrm{H}\right)$$$ NMR spectrum. .................................................................................................................................

Chemistry

IGCSE&ALevel

CAIE

Exam No：9701_s24_qp_41 Year：2024 Question No：7(c)

Answer:

Knowledge points:

37.4.1.1 the different environments of proton present using chemical shift values

37.4.1.2 the relative numbers of each type of proton present from relative peak areas

37.4.1.3 the number of equivalent protons on the carbon atom adjacent to the one to which the given proton is attached from the splitting pattern, using the n + 1 rule (limited to singlet, doublet, triplet, quartet and multiplet)

37.4.1.4 the possible structures for the molecule

37.4.2 predict the chemical shifts and splitting patterns of the protons in a given molecule

37.4.3 describe the use of tetramethylsilane, TMS, as the standard for chemical shift measurements

37.4.4 state the need for deuterated solvents, e.g. CDCl 3, when obtaining a proton NMR spectrum

37.4.5 describe the identification of O–H and N–H protons by proton exchange using D2O

Answer:

Knowledge points:

Solution:

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