Rate constants for electron transfer reactions involving single walled carbon nanotubes should vary with the chirality vector (n,m). To date, the functional form of this relationship has proven elusive. We have performed completely automated reactions of single walled carbon nanotubes (SWNT) with 4-hydroxybenzene diazonium salt under various experimental conditions, and analyzed their influence on the reaction selectivity using UV-vis-nIR absorption spectroscopy and a previously published spectral deconvolution procedure. The selectivity of the reagent to metallic SWNT over semiconducting SWNT was greater at low salt concentrations (73%) and lower at high salt concentrations (54%). The activity of diazonium was increased upon illumination; however, similar rate constants for the SWNT (relative to the (11,5) nanotube) were computed for the light and dark reactions, indicating that the type of diazonium intermediate affects the extent of reaction and not the rate. The steady state data has been modeled using an adsorption-reaction scheme, and an electron transfer theory is developed to yield the first structure-reactivity relationship for SWNT.