Glycine methyl ester hydrochloride

The title compound [systematic name: (methoxycarbonylmethyl)ammonium chloride], crystallizes as a salt, C3H8NO2 +·Cl−, with the charged species interacting mutually via strong and highly directional N+—H⋯Cl− hydrogen bonds which lead to the formation of a supramolecular tape running parallel to the c axis. Tapes close pack in the solid state mediated by multipoint recognition synthons based on weak C—H⋯O interactions and van der Waals contacts between adjacent methyl groups.

The title compound [systematic name: (methoxycarbonylmethyl)ammonium chloride], crystallizes as a salt, C 3 H 8 NO 2 + ÁCl À , with the charged species interacting mutually via strong and highly directional N + -HÁ Á ÁCl À hydrogen bonds which lead to the formation of a supramolecular tape running parallel to the c axis. Tapes close pack in the solid state mediated by multipoint recognition synthons based on weak C-HÁ Á ÁO interactions and van der Waals contacts between adjacent methyl groups.
Data collection: APEX2 (Bruker, 2006); cell refinement: SAINT-Plus (Bruker, 2005); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: DIAMOND (Brandenburg, 2009); software used to prepare material for publication: SHELXTL.  (Shi et al., 2008;Paz & Klinowski, 2003;Paz et al., 2002), we recently started to prepare novel organic ligands based on amino acid moieties, which can be ultimately employed as building units in the construction of multi-dimensional coordination polymers. Even though the latest release of the Cambridge Structural Database (CSD, Version of November 2008 with three updates; Allen, 2002) contains the remarkable number of 70 determinations of zwiterionic glycine, the structure of the title compound has never been reported to date. It is important to emphasize that crystallization of this compound is not trivial, typically leading to microcrystalline powders with needle-like crystal habit. Larger single crystals could only be obtained when a 1: 1 chloroform: methanol mixture was used (Fig. 1).

Structure Reports Online
The asymmetric unit of the title compound, (I), is composed of a cationic glycinium methyl ester moiety and a chloride anion as depicted in Fig. 2. In the crystal structure, the three crystallographically independent N-H moieties are engaged in strong and highly directional [<(DHA) greater than 140°] N + -H···Clhydrogen bonds with three symmetry-related Clanions (Fig. 3). These interactions promote the formation of a tape of C 3 H 8 NO 2 +.
Clmoieties running parallel to the c axis. It is noteworthy to emphasize that the N + -H···Clinteractions can be divided into two families according to the registered d D···A distances: while the two outer interactions of the tape have interatomic distances ranging from 3.112 (4) to 3.112 (4) Å, the inner hydrogen bond is weaker with the corresponding value being 3.269 (4) Å. Indeed, FT-IR studies on the title compound support this assumption clearly revealing the presence of two stretching bands centered at ca 2628 and 2682 cm -1 and attributed to two ν(N + -H) families, respectively.
Clchains close pack in the solid state mediated by a combination multipoint recognition synthons involving weak C-H···O hydrogen bonds (not shown; Nangia & Desiraju, 1998) and the need to effectively fill the available space (i.e., van der Waals interactions; Fig. 4). This packing behavior is strikingly distinct from that reported by Handelsman-Benory et al. (1995): while in (I) all H atoms bound to nitrogen are engaged in N + -H···Clinteractions, in glycyl-glycyl-glycine methyl ester hydrochloride the N-H and C=O moieties from the middle of the chain establish further hydrogen bonding connections with neighboring molecules; the final connectivity of the compounds results in a three-dimensional network of strong and highly directional hydrogen bonds.

Experimental
Glycine methyl ester hydrochloride (99% purity) was purchased from Sigma-Aldrich and used without further purification.
Crystalline material suitable for single-crystal studies (Fig. 1) was isolated from the slow evaporation (at ambient temperature) of a 1: 1 chloroform: methanol solution.

Refinement
Hydrogen atoms bound to nitrogen and carbon were located at their idealized positions and were included in the final structural model in riding-motion approximation with C-H = 0.98 Å and N-H = 0.91 Å. The isotropic thermal displacement parameters for these atoms were fixed at 1.2 (for the -CH 2 -group) or 1.5 (for the pendant -NH 3 + and -CH 3 moieties) times U eq of the atom to which they are attached.    Table 1. Symmetry transformations used to generate equivalent atoms: (i) x, -y + 1/2, z+1/2; (ii) x, y, z+1.  Geometric parameters (Å, °)