title: A structural and spectroscopic investigation of the hydrochlorination of 4,4'-methylenedianiline.
abstract: The hydrochlorination of 4,4'-methylenedianiline, NH(2)C(6)H(4)CH(2)C(6)H(4)NH(2) (MDA), in chlorobenzene to produce 4,4'-methylenedianiline dihydrochloride, [H(3)NC(6)H(4)CH(2)C(6)H(4)NH(3)]Cl(2) (MDA x 2 HCl) is an important reaction for the production of isocyanates, which are used to manufacture polyurethanes. This reaction is examined here. MDA is moderately soluble in chlorobenzene, whereas MDA x 2 HCl is effectively insoluble. Controlled addition of anhydrous HCl to MDA in chlorobenzene led to the isolation of a solid whose stoichiometry is MDA x HCl. Crystals obtained from solutions of MDA x HCl in methanol were found by X-ray analysis to consist of the basic hydrochloride salt, [MDAH(2)][Cl](2)[MDA](2)H(2)O, which is stabilised by complex hydrogen-bonding. The starting material MDA has an H-bonded structure in which the molecules are linked in a one-dimensional chain. Hydrogen-bonding is extensive in MDA x 2 HCl which contains ladders of [H(3)NC(6)H(4)CH(2)C(6)H(4)NH(3)](2+) dications stabilised by N-H...Cl linkages. Energy calculations on the crystalline systems allow an identification of the main factors in intermolecular cohesion; these are related to melting temperature and solubility data. Such improvements in understanding of solute-solute interactions are prerequisites for improving the atom economy of this important stage within the polyurethane manufacture process chain. The solid phase IR spectrum of MDA x 2 HCl is diagnostic, principally as a result of a Fermi resonance process.
authors.affiliation: Department of Chemistry, Joseph Black Building, University of Glasgow, Glasgow, Scotland, UK G12 8QQ.
authors.forename: Emma K
authors.initials: EK
authors.lastname: Gibson
authors.forename: John M
authors.initials: JM
authors.lastname: Winfield
authors.forename: Kenneth W
authors.initials: KW
authors.lastname: Muir
authors.forename: Robert H
authors.initials: RH
authors.lastname: Carr
authors.forename: Archie
authors.initials: A
authors.lastname: Eaglesham
authors.forename: Angelo
authors.initials: A
authors.lastname: Gavezzotti
authors.forename: David
authors.initials: D
authors.lastname: Lennon