During nitration of benzene, a nitro group replaces a carbon atom. Give the shape (geometry) around the carbon that is substituted: • in the benzene molecule, • in the intermediate complex, • in the nitrobenzene product.
Naphthalene, $\text{C}_{10}\text{H}_8$, is an arene hydrocarbon. On nitration of naphthalene, two organic products are formed in a mixture. Each product contains one nitro group. Propose the structures of these compounds.
Under suitable conditions, naphthalene can be oxidised to phthalic anhydride, $\text{C}_8\text{H}_4\text{O}_3$, carbon dioxide and water. Write an equation for this reaction. Represent an oxygen atom from the oxidising agent by $[\text{O}]$.
Phenolphthalein, the indicator, can be prepared from phthalic anhydride and phenol under suitable conditions, with water as a product. Deduce the type of reaction shown by this equation.
State the functional groups present in a phenolphthalein molecule, excluding the benzene ring.
Phenolphthalein is reacted separately with the two reagents listed in the table. Fill in the table by drawing the organic products formed (with part of each structure already given) and by naming the reaction types.
Phenolphthalein acts as an indicator and is shown by the formula $\text{HIn}$. Phenolphthalein, $\text{HIn}$, behaves as a weak acid. $\text{HIn} \rightleftharpoons \text{H}^+ + \text{In}^-$ For phenolphthalein, $K_a = 5.0 \times 10^{-10}~\text{mol dm}^{-3}$ at $298~\text{K}$. Its colour change occurs at about pH $8.8$. Calculate the ratio $\frac{[\text{In}^-]}{[\text{HIn}]}$ at pH $8.8$.
On the methyl orange structure, circle the bond or bonds that give this compound its dye properties.
Methyl orange changes colour between pH $3.2$ and pH $4.4$. Suggest the structure of methyl orange at pH $3.0$. Assume the $-\text{SO}_3^-\text{Na}^+$ group does not react.
Methyl orange is made as shown. Deduce the identities of compounds R and S and draw their structures in the boxes.
Suggest the reagents and conditions used in step 1 and step 2.