MOLECULAR WEIGHTS OF NONHALO- BENZENES

THE MOLECULAR WEIGHT DISCUSSED HERE IS THE ONE OBTAINED FROM ISOTOPICALLY AVERAGED ATOMIC WEIGHTS.

IN THE CASE OF BENZENES WITHOUT HALOGEN SUBSTITUTION, THE MOLECULAR WEIGHT IS RELATIVELY CLOSE TO THE AVERAGE OF MAXMASS AND HIMAX1. THESE SPECTRAL PARAMETERS ARE DISCUSSED BELOW. IN 95% OF THESE CASES THE UPPER LIMIT FOR THE MOLECULAR WEIGHT IS WITHIN 21 DALTONS ABOVE THE AVERAGE. IN 99% OF THE COMPOUNDS THE UPPER LIMIT IS WITHIN 56 DALTONS ABOVE THE AVERAGE.

TYPES OF SUBSTITUTED BENZENES INCLUDED IN THESE UPPER LIMITS ARE ALKYL, ALKENYL, AND ALKYNYL SUBSTITUTED, CYCLIC AND ACYCLIC BENZENES.  ALSO INCLUDED ARE PHENYL ALDEHYDES AND KETONES. THERE ARE ALSO CYANO AND ALKYL AS WELL AS ALKENYLCYANO BENZENES. NO BIPHENYLS NOR NITRO BENZENES ARE INCLUDED. THE HIGHEST MOLECULAR WEIGHT OF ALL THESE COMPOUNDS WAS 218 DALTONS.

FOR A LOWER LIMIT TO THE MOLECULAR WEIGHT GO HERE.

MAXMASS-HIMAX1 AVERAGE

1. FIND THE HIGHEST MASS IN THE SPECTRUM WITH AN INTENSITY OF 5% OF THE BASE PEAK.  THIS IS DESIGNATED AS MAXMASS.

2. FIND THE HIGHEST MASS IN THE SPECTRUM WITH AN INTENSITY OF 1% OF THE BASE PEAK.  THIS IS CALLED HIMAX1.

3. TAKE THE AVERAGE OF THESE TWO MASSES. THEY MAY BE IDENTICAL, BUT HIMAX1 MUST BE GREATER THAN OR EQUAL TO MAXMASS.

SEE EXAMPLE BELOW

MAXMASS = 195 DALTONS

HIMAX1 = 195 DALTONS