Bond energies chlorine-phosphorus

These values correspond to the average energy 240 kJ mole for the C1=0 bond, 485 kJ mole for the S=b- bond, and 620 kJ mole for the P=0 bond the increase from chlorine to phosphorus is... 

Potential energy surfaces for nucleophilic displacements at phosphorus in dimethyl methyl-, chloromethyl-, dichloromethyl-, and trichloromethyl-phosphonates were computed by DFT methods. The results revealed that sequential introduction of chlorine substituents at the methyl group of a methylphosphonate diester increased the stability of TSs and intermediates leading to P-C bond cleavage. Indeed, the trichlorinated analogue (23) reacted with NaOMe exclusively via P-C bond dissociation to form dichlorocarbene, which was trapped by various alkenes to form the corresponding gem-dichlorocyclopropanes (24) (Scheme... 

The elements to the right of silicon are all non-metallic elements. They exist as relatively small molecules. Sulfur exists as Sg molecules, phosphorus as molecules and chlorine as Cl molecules. Although the covalent bonds within each molecule are strong, there are only relatively weak van der Waals forces between their molecules (see page 62). Therefore, it does not take much energy to break these weak intermolecular forces and melt the elements. At room temperature, phosphorus and sulfur are solids with low melting points and chlorine is a gas. 

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