State the meaning of partition coefficient, $K_{pc}$.
The partition coefficient, $K_{pc}$, for a compound, $X$, between carbon disulfide, $\text{CS}_2$, and water is $10.5$. $1.85\ \text{g}$ of $X$ is dissolved in water and made up to $100.0\ \text{cm}^3$ in a volumetric flask. $40.0\ \text{cm}^3$ of this aqueous solution is shaken with $25.0\ \text{cm}^3$ of $\text{CS}_2$. The mixture is allowed to reach equilibrium. Calculate the mass of $X$, in $\text{g}$, extracted into the $\text{CS}_2$ layer.
The compound $\text{C}_6\text{H}_6$ has many structural isomers. Four possible structures of $\text{C}_6\text{H}_6$ are shown in Fig. 6.1. Using Fig. 6.1, complete Table 6.1 to predict how many carbon atoms in Kekulé benzene, Dewar benzene and Ladenburg benzene are $sp$, $sp^2$ and $sp^3$ hybridised.
Describe the shape of delocalised benzene. Include the geometry around each carbon, the C-C-H bond angle and the type of bond(s) between carbon atoms and between carbon and hydrogen atoms.
Suggest why Dewar benzene and Ladenburg benzene are unstable isomers of $\text{C}_6\text{H}_6$.
Complete Table 6.2 to predict how many peaks appear in the proton ($^1\text{H}$) NMR spectrum for Dewar benzene, Ladenburg benzene and delocalised benzene.
The reaction of phenylethanone with $1,4$-dibromobutane, $\text{BrCH}_2\text{CH}_2\text{CH}_2\text{CH}_2\text{Br}$, in the presence of $\text{FeBr}_3$ is shown in Fig. 6.2. The mechanism for this reaction is similar to the alkylation of benzene. Construct an equation for the formation of the electrophile, $\text{BrCH}_2\text{CH}_2\text{CH}_2\text{CH}_2^+$.
Complete the mechanism in Fig. 6.3 for the reaction of phenylethanone with $\text{BrCH}_2\text{CH}_2\text{CH}_2\text{CH}_2^+$ ions. Include all relevant curly arrows and charges. Draw the structure of the organic intermediate.
The reaction shown in Fig. 6.2 produces small quantities of two by-products, $Y$ ($\text{C}_{20}\text{H}_{22}\text{O}_2$) and $Z$ ($\text{C}_{12}\text{H}_{14}\text{O}$). Suggest structures for $Y$ and $Z$ in the boxes in Fig. 6.4.