effect of alkyl substituents on the hydrogen bonding and molecular structure of benzophenylhydroxamic acids crystal structure of uo2 complex of p-isopropylbenzophenylhydroxamic acid

the effect of alkyl substituents on the c-phenyl and/or the n-phenyl ring of benzophenylhydroxamic acid on their molecular structure and hydrogen bonding has been investigated. the predominant configuration in chcl3 is determined by steric and electronic effects. substituents on the c-phenyl ring favor the cis configuration, while substituents in the n-phenyl ring favor a trans configuration. these can be rationalized on the basis of electronic effects. bulky substituents in the c-phenyl ring give rise to a mixture of cis and trans forms due to steric factors. when substituents are present on the c-phenyl ring and n-phenyl ring the trans configuration is preferred. the crystal and molecular structures of  complex of p-isopropylbenzophenylhydroxamic acid have been determined from a single crystal of this complex to elucidate the effect of complexation on the structure of this ligand which exists as a cistrans mixture. complexation occurs exclusively from the cis configuration.