Pure Quadrupole Resonances in Multichlorobenzenes

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Abstract
The location and measurement of the nuclear quadrupole resonances of Cl35 in all multichlorobenzenes has been completed with the detection of resonance frequencies in five such compounds. A summary of the data on all the multichlorobenzenes is presented, including these reported for the first time: 1,2,3‐trichlorobenzene; 1,3,5‐trichlorobenzene; 1,2,3,4‐tetrachlorobenzene; 1,2,3,5‐tetrachlorobenzene; and pentachlorobenzene. These data indicate that the chlorine resonance frequency acquires frequency increments approximately proportional to the number of ortho chlorine neighbors. This effect may be interpreted primarily in terms of electron induction away from the resonant chlorine, although out of plane bending and double bond character also affect the resonance frequency. A correlation of the chlorine quadrupole frequencies with the Hammett sigma parameter is also given.