1-(Aminomethyl)cyclohexan-1-ol is treated with $\mathrm{NaNO}{}_2$/dilute $\mathrm{HCl}$ at 273 K (Tiffeneau-Demjanov type ring expansion). The major carbonyl product is

The primary amine gives a diazonium ion, which loses $\mathrm{N}{}_2$ as the leaving group. A ring carbon migrates from the carbinol carbon to the electron-deficient $\mathrm{CH}{}_2$, expanding the ring from six to seven members. Loss of the OH proton then gives cycloheptanone.