Quantum chemical study of hydrogen-bonded CH2=C=O center dot center dot center dot HX and CH2=C=CH2 center dot center dot center dot HX (X=Cl, F) complexes

An ab initio quantum chemical study, largely at the 6-311 + + G**/MP2 = full level of theory has been carried out on the 1:1 and 2:1 complexes of HX (X = Cl, F) with ketene and are compared with the corresponding isoelectronic complexes of H2C=C=CH2 and HX. Three possible modes of the hydrogen bond between HX and ketene via the dipole-induced dipole (X-H ... C, X-H ... O) and the weak X-H ...pi interactions were considered. The binding energy has been calculated after giving careful consideration to basis set superposition effects and zero-point vibrational energy effects. The electron correlation correction to the binding energy has also been computed. Weak X-H ...pi hydrogen bonds are perhaps possible with nonpolar C=C and C=C pi-clouds.