RACEMIC COMPOUND FORMATION CONGLOMERATE FORMATION .3. INVESTIGATION OF THE ACIDIC SALTS OF ALPHA-PHENYLETHYLAMINE BY ACHIRAL DICARBOXYLIC-ACIDS - OPTICAL RESOLUTION BY PREFERENTIAL CRYSTALLIZATION AND A STRUCTURAL STUDY OF (R)-ALPHA-PHENYLETHYLAMMONIUM HYDROGEN ITACONATE

Acidic salts of eight achiral dicarboxylic acids with alpha-phenylethy lamine are prepared and investigated by IR and density measurements, a nd X-ray crystallography to distinguish between racemic compound and c onglomerate formation, It was found that conglomerate formation takes place when the protonated and deprotonated carboxylic groups form hydr ogen bonded chains rather than forming cyclic intramolecular hydrogen bonds, Racemic compound formation, and indeed intramolecular IT-bond f ormation, seems to be preferred when the two carboxylates are constrai ned in the same plane close to each other by a double bond, or they ar e ortho-substituents of a planar ring, The rules found for conglomerat e formation of acidic salts of alpha-phenylethylamine are compared wit h Saigo's rules for conglomerate formation. The crystal structure of t he conglomerate forming (R)-alpha-phenylethylammonium hydrogen itacona te is (OARPHI) also presented and the optical resolution by preferenti al crystallization is described, The hydrogen bonding network of OARPH I [N-1 = C(7)C-2(2)(6), N-2 = R(3)(3)(8)R(5)(5)(22)] is very similar t o the hydrogen bonding network of the other conglomerate forming salt of this series:alpha-phenylethylammonium hydrogen succinate [N-1 = C(7 )C-2(2)(9), N-2 = R(3)(3)(8)R(3)(3)(13)].