H-Bonding-Induced Repulsion Between Small Groups Toward a Highly Puckered Benzene.

Benzene ring puckering generally arises from the strong repulsion between bulky substituents, while in this study, we present that benzene ring puckering can be achieved by repulsion between small substituents (nitro and methyl groups) facilitated by hydrogen-bonding attraction, as exemplified in 1,3,5-trinitro-2,4,6-trimethylaminobenzene. The role of intramolecular hydrogen bonding and steric repulsion is further investigated through comparison with four structurally related compounds differing in hydrogen-bond donor availability and substituent size.