Describe structural isomerism.

1. (a)Describe structural isomerism.[1]
2. (b)(i)A and B are structural isomers with molecular formula C5H10O. They are both straight-chained molecules with only one functional group. Table 5.1 describes observations when separate samples of A and B are added to different reagents. Table 5.1 reagent | A | B ---|---|--- 2,4-dinitrophenylhydrazine (2,4-DNPH reagent) | orange precipitate appears | orange precipitate appears Tollens' reagent | silver mirror appears | no reaction alkaline I2(aq) | no reaction | no reaction Name the functional group present in both A and B.[1]
3. (b)(ii)Draw the structures of A and B in the boxes. A B[2]
4. (c)(i)C is a structural isomer of A and B. C is straight chained and has two functional groups. C shows only one type of stereoisomerism. Table 5.2 describes observations when separate samples of C are added to different reagents. Table 5.2 reagent | C ---|--- 2,4-dinitrophenylhydrazine (2,4-DNPH reagent) | no reaction Br2(aq) | orange to colourless alkaline I2(aq) | yellow precipitate appears Draw the structure of C in the box. C[2]
5. (c)(ii)Name the type of stereoisomerism shown by molecules of C.[1]
6. (d)(i)D reacts in the presence of a sulfuric acid catalyst to form E and water. The structure of E is shown in Fig. 5.1. [Figure 5.1] Name the functional group present in E.[1]
7. (d)(ii)Identify the type of reaction that occurs when D reacts to form E.[1]
8. (d)(iii)Draw the structure of D in the box. D[1]
9. (d)(iv)The infrared spectrum of E is shown in Fig. 5.2. [Figure 5.2] Table 5.3 bond | functional groups containing the bond | characteristic infrared absorption range (in wavenumbers)/cm⁻¹ ---|---|--- C-O | hydroxy, ester | 1040–1300 C=C | aromatic compound, alkene | 1500–1680 C=O | amide | 1640–1690 carbonyl, carboxyl | 1670–1740 ester | 1710–1750 C≡N | nitrile | 2200–2250 C-H | alkane | 2850–2950 N-H | amine, amide | 3300–3500 O-H | carboxyl | 2500–3000 hydroxy | 3200–3600 Use Fig. 5.2 and Table 5.3 to predict two differences in the absorptions above 1500cm⁻¹ of the infrared spectrum of D compared to E. Explain your answer.[2]

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