Radical species formed by H atom extraction from methane

7 Radical species formed by H atom extraction from methane 

Progressive removal of hydrogen atoms from methane yields the radicals CH3 (methyl), CH2 (methylene), and CH (methylidyne). These very unstable species may be studied in electric discharges. The C-H bond distances and bond dissociation energies are listed in Table 13.3 

The methyl radical contains one unpaired electron. The coordination geometry is trigonal planar, and the unpaired electron occupies the orbital on C. (Remember that the direction 

The methylene radical offers another surprise the ground state is a triplet, i.e. it contains two unpaired electrons with parallel spins The electronic structure is therefore different from that of CCI2 which, as we have seen, contains a non-bonding electron pair in an sp hybrid AO on the C atom. In the ground state of CH2 one non-bonding electron remains in 

The spi and py atomic orbitals in CH2 are, of course not degenerate, and accurate quantum chemical calculations [3] indicate that it requires 96 kJ mol excite molecules from the spi to the sp p1 configuration if the spins remain antiparallel. The energy released when their spin are changed from antiparallel to parallel is, however, so large (133 kJ mol ) that the triplet becomes the ground state. 

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