State what is meant by partition coefficient, Kpc.

1. (a)(i)State what is meant by partition coefficient, Kpc.[1]
2. (a)(ii)The partition coefficient, Kpc, for a compound, X, between carbon disulfide, CS₂, and water is 10.5. 1.85 g of X is dissolved in water and made up to 100.0 cm³ in a volumetric flask. 40.0 cm³ of this aqueous solution is shaken with 25.0 cm³ of CS₂. The mixture is left to reach equilibrium. Calculate the mass of X, in g, extracted into the CS₂ layer. mass of X = g[2]
3. (b)The compound C₆H₆ has many structural isomers. Four suggested structures of C₆H₆ are shown in Fig. 6.1. [Figure 6.1] Using Fig. 6.1, complete Table 6.1 to predict the number of carbon atoms that have sp, sp² and sp³ hybridisation in Kekulé benzene, Dewar benzene and Ladenburg benzene. [Table 6.1][2]
4. (c)Describe the shape of delocalised benzene. Include the geometry of each carbon, the C-C-H bond angle and the type of bond(s) between the carbon atoms and between the carbon and hydrogen atoms.[2]
5. (d)Suggest why Dewar benzene and Ladenburg benzene are unstable isomers of C₆H₆.[1]
6. (e)Complete Table 6.2 to predict the number of peaks in the proton (¹H) NMR spectrum for Dewar benzene, Ladenburg benzene and delocalised benzene. [Table 6.2][1]
7. (f)(i)The reaction of phenylethanone with 1,4-dibromobutane, BrCH₂CH₂CH₂CH₂Br, in the presence of FeBr₃ is shown in Fig. 6.2. [Figure 6.2] The mechanism of this reaction is similar to that of the alkylation of benzene. Construct an equation for the formation of the electrophile, BrCH₂CH₂CH₂CH₂⁺.[1]
8. (f)(ii)Complete the mechanism in Fig. 6.3 for the reaction of phenylethanone with BrCH₂CH₂CH₂CH₂⁺ ions. Include all relevant curly arrows and charges. Draw the structure of the organic intermediate. [Figure 6.3][3]
9. (f)(iii)The reaction shown in Fig. 6.2 forms small amounts of two by-products, Y (C₂₀H₂₂O₂) and Z (C₁₂H₁₄O). Suggest structures for Y and Z in the boxes in Fig. 6.4. [Figure 6.4][2]

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