Monoclinic form of ethyl 4-aminobenzoate (benzocaine)

Abstract

The structure of the title compound, C9H11NO2, (I), comprises a flat mol­ecule arranged, head‐to‐tail, in linear ribbon arrays via a N—H⋯O=C association. These ribbons end‐on form a herring‐bone structure interconnected via N—H⋯N association. The structure was first determined in 1987 [Sinha & Pattabhi (1987). Proc. Indian Acad. Sci. Chem. Sci. 98, 229–234] in the orthorhombic space group P212121, with R = 0.120, whereas similar cell dimensions and an increased β angle in the present study resulted in monoclinic space group P21/c, with R = 0.065.

Single-crystal diffuse scattering studies on polymorphs of molecular crystals. I. The room-temperature polymorphs of the drug benzocaine

“…This and the fact that crystals suitable for diffuse scattering studies can readily be grown make it an ideal compound for this type of study. Room-temperature single-crystal X-ray diffraction studies reveal the existence of two polymorphs for BZC, one crystallizing as monoclinic P2 1 =c [polymorph (I); Lynch & McClenaghan, 2002], the other as orthorhombic P2 1 2 1 2 1 [polymorph (II); Sinha & Pattabhi, 1987]. As a result of the present studies a third low-temperature polymorph [polymorph (III)] has been found.…”

A new high-pressure benzocaine polymorph — towards understanding the molecular aggregation in crystals of an important active pharmaceutical ingredient (API)

“…Until now three polymorphs of BZC were known. At ambient conditions, BZC exists in two forms: monoclinic polymorph (I) (space group P2 1 /c, Lynch & McClenaghan, 2002) and orthorhombic polymorph (II) (space group P2 1 2 1 2 1 ; Sinha & Pattabhi, 1987). On cooling to 150 K, polymorph (II) undergoes a solid-to-solid phase transition to polymorph (III) of monoclinic symmetry, space group P112 1 (Chan et al, 2009).…”

The Role of Molecular Structure in the Crystal Polymorphism of Local Anesthetic Drugs: Crystal Polymorphism of Local Anesthetic Drugs, Part X

“…I, and SLC hydrate suitable for SCXRD could be produced, and the crystal structures were determined. The crystal structures of local anesthetics, which were known before this study [BZC (36,37), procaine (PC) (38), PCHC (39,40), dyclonine hydrochloride (DCNHC) (41), LDCHC hydrate (42), BPCHC (43), BPCHC ethanolate, R-BPCHC (44), and mepivacaine hydrochloride (MPCHC) (45)], gave no indication on conformational polymorphism (Table IV) because they all show just one conformation of the molecule [except the monomorphic LAA compounds lidocaine (LDC) (46) and cinchocaine hydrochloride hydrate (CCCHC) (47,48), which consist of two conformers in the asymmetric unit]. The polymorphic crystal structures of this study confirm that the crystal polymorphism of these compounds is caused by the conformational flexibility of the molecules (see Structural Aspects).…”