tert-Butyl 2-benzoyl-2-methyl-propanoate.

The title compound, C(15)H(20)O(3), is bent with a dihedral angle of 67.28 (9)° between the mean planes of the phenyl ring and a group encompassing the ester functionality (O=C-O-C). In the crystal, mol-ecules related by inversion symmetry are connected by weak C-H⋯O inter-actions into infinite chains. On one side of the mol-ecule there are two adjacent inter-actions between neighbouring mol-ecules involving the H atoms of methyl groups from the dimethyl groups and the O atoms of the ketone; on the other side, there are also two inter-actions to another adjacent mol-ecule involving the H atoms on the phenyl rings and the carbonyl O atoms of the ester functionality.

tert-Butyl 2-methyl-2-(4-methyl-benzo-yl)propanoate.

The title compound, C(16)H(22)O(3), is bent with a dihedral angle of 75.3 (1)° between the mean planes of the benzene ring and a group encompassing the ester functionality (O=C-O-C). In the crystal, the mol-ecules are linked into infinite chains held together by weak C-H⋯O hydrogen-bonded inter-actions between an H atom on the benzene ring of one mol-ecule and an O atom on the ketone functionality of an adjacent mol-ecule. The chains are arranged with neighbouring tert-butyl and dimethyl groups on adjacent chains exhibiting hydro-phobic stacking, with short C-H⋯H-C contacts (2.37 Å) between adjacent chains.

tert-Butyl 2-(4-chloro-benzo-yl)-2-methyl-propanoate.

The title compound, C(15)H(19)ClO(3), is bent with a dihedral angle of 72.02 (9)° between the mean planes of the benzene ring and a group encompassing the ester functionality (O=C-O-C). In the crystal, mol-ecules related by inversion symmetry are connected by weak C-H⋯O inter-actions into infinite chains. These inter-actions involve H atoms from a methyl group of the dimethyl residue and the O atoms of the ketone on one side of a mol-ecule; on the other side there are inter-actions between H atoms of the benzene ring and the carbonyl O atoms of the ester functionality. There are no directional inter-actions between the chains.

tert-Butyl 2-methyl-2-(4-nitro-benzo-yl)propanoate.

The title compound, C(15)H(19)NO(5), is bent with a dihedral angle of 61.8 (2)° between the mean planes of the benzene ring and a group encompassing the ester functionality (O=C-O-C). The dihedral angle of 0.8 (2)° between the mean planes of the nitro group and the benzene ring indicates near coplanarity. In the crystal, each mol-ecule is linked to four adjacent mol-ecules by weak C-H⋯O hydrogen-bonding inter-actions. Both benzene H atoms ortho to the ketone O atom form C-H⋯O hydrogen bonds with the keto O atoms of two neighboring mol-ecules (of the keto and ester groups, respectively), and the two other inter-actions involve the H atoms from a methyl group of the dimethyl residue, displaying C-H⋯O inter-actions with the O atoms of the nitro groups. These four inter-actions for each mol-ecule lead to the formation of two-dimensional sheets with a hydro-philic inter-ior, held together by weak hydrogen-bonded inter-actions, and a hydro-phobic exterior composed of protruding methyl groups which interst-ack with the methyl groups in adjacent sheets.