The crystal and molecular structures of iminodiacetic acid hydrochloride, C4H7NO4.HCl and iminodiacetic acid hydrobromide, C4H7NO4.HBr

Abstract

The crystal and molecular structures of iminodiacetic acid hydrochloride, C4H7NO4. HC1, and iminodiacetic acid hydrobromide, C4H7NO4.HBr, have been determined by a symbolic addition method with three-dimensional single crystal X-ray data obtained on a diffractometer. The compounds are isostructural, crystallizing in the orthorhombic space group Pmmn with Z= 2. The unit-cell dimensions are a= 12.4101, b= 5.7349, c=5.1280 A~ and a= 12.8150, b= 5.8705, e=5.0870/~ for the chloride and bromide respectively. Positively charged iminodiacetic acid ions are connected by hydrogen bonds via the halide ions and zigzag layers are formed. These layers are stacked in the c direction and the forces between the layers are of van der Waals type.

Combined X-ray and neutron diffraction studies of normal and deuterated iminodiacetic acid hydrobromide

“…The crystal data are taken from Oskarsson (1973). The volume of the crystal used in the data collection was 9.42 mm a and it had eight well formed faces.…”

“…X-ray intensities were collected on a computer-controlled four-circle diffractometer of type CAD-4. Experimental conditions and data reduction were as described previously (Oskarsson, 1973) with one exception: the scan interval, Aco, was extended 25% at both ends for background measurement with moving crystal and detector. All 430 reflexions in the range 5 ° < 0 < 70 ° were measured.…”

“…The structure of iminodiacetic acid hydrobromide (IDAB) has been studied previously by X-ray diffraction (Oskarsson, 1973). The present work was undertaken to determine the H positions in IDAB and the D positions in deuterated iminodiacetic acid hydrobromide (DIDAB), in order to study the geometry of the bonds N-H. to use the atomic coordinates obtained in the neutron studies for analyses of the X-ray intensity data sets to illustrate the electron density within the organic ion and in the hydrogen bonds.…”

“…The theoretical models for this phenomenon have often been based on the assumption that potential energy curves or surfaces are unaffected by isotopic substitution. The structures of normal and deuterated iminodiacetic acid hydrochloride have been studied previously by X-ray methods (Oskarsson, 1973(Oskarsson, , 1974c. It was concluded that the two hydrogen bonds N-H...CI and O-H...CI are shortened on deuteration and as a consequence the potential energy curves for both N-H...CI and O-H...CI are affected by isotopic substitution in this compound.…”

“…In a systematic study of the geometry of the positively charged iminodiacetic acid ion, [CaHsNO4] +, the structures of the addition compounds of iminodiacetic acid with the hydrogen halides have been determined from X-ray intensities (Oskarsson, 1973(Oskarsson, , 1974a. They contain chains of positively charged iminodiacetic acid ions and halide ions, linked by hydrogen bonds into layers.…”