Surface Reactivity for Chlorination on Chlorinated (5,5) Armchair SWCNT: A Computational Approach

In the present work, we first attached one chlorine radical and then examined the site selectivity for the addition of a second chlorine radical on the external surface of (5,5) armchair single-walled carbon nanotubes (SWCNTs) of 9 and 15 carbon layers. Optimized geometries and energetics were determined using density functional theory (DFT), at the M06-2X/6-31G(d,p) level. Computed reaction energy values for second chlorination have been used to corroborate the prediction of the reactivities of different sites based on the electron density distribution in the singly occupied molecular orbital (SOMO), total spin density, the DFT based local reactivity descriptors (viz., Fukui function, local softness), and the average local ionization energy. Natural bond orbital (NBO) analysis was performed to confirm the covalent bonding between the chlorine and carbon of the SWCNT. The present study reveals that the first chlorine attached to the SWCNT behaves like an ortho- and para-director. The addition of a second chlorine on an already chlorinated SWCNT exhibits positional preference.