CCL:G: Tautomeric equilibrium

 Sent to CCL by: "Serdar  Badoglu" [sbadoglu-$-gazi.edu.tr]
 Dear CCL'ers,
 This will be little long message, sorry.
 I'm studying on a heterocyclic compound which exhibits tautomerism, and every
 tautomer has its several conformations. The experimental data I have are from
 the IR, and Ra. I have computed the geometrical parameters and vibrational
 frequencies of every single conformer in the gas phase by using Gaussian 03.
 After putting the Gibbs free energy values (obtained from that
 calculations)into Boltzmann distribution, I have found that %67 population
 for Tautomer 1 (one conformer >%1) and %33 pop for Tautomer 2 (one conformer
 >%1). So I have decided to interpret the experimental vibrational spectra
 (belong to solid phase) according to these two conformers. When I found
 several bands remained still unassigned, I have considered dimerization in
 solid phase. Then calculated the possible dimers of the compound (again in
 gas phase), and seen that unassigned bands are computed in dimers'
 frequencies. So I have concluded that the sample may contain both tautomers
 and a dimeric structure. At this point I need to say that I couldn't be able
 to assign all the experimental bands to a single structure (and be informed
 that the peaks in the experimental IR spectrum are not sharp. You may guess
 the rest, I'm pretty sure that you have read many such studies published in
 many journals.
 Recently I have a message from a journal's editor, and the comments of one of
 the reviewers are puzzled me. And that's why I'm writing all of these. I need
 your opinion.
 First, he/she claims that the calculations for gas phase are useless since
 the compound is in solid phase. He/she says that instead of doing it in this
 way I should solve the crystal structure (I couldn't obtain crystals of this
 compound). He/she suggests that otherwise assignments should be done only and
 unequivocally to one tautomer (which seems improbable to me).
 Second, he/she claims that the Boltzmann distribution cannot be used in my
 case because my tautomers don't seem in equilibrium to him/her. Also he/she
 says that I cannot apply gas phase BD to crystalline phase sample (I know
 this. I had some 30 possible conformers and I was just trying to eliminate
 themi that's all.). Furthermore, he/she says that the relative amounts of the
 tautomers in gas phase would depend on the way the vapor is produced (in this
 case I think that if the composition depends on the way of vapor production,
 then using BD for gas phase is also useless??).
 Finally, he/she has found my conclusion of coexistance of two tautomers and a
 dimer is not plausible.
 So, I wonder what you think.
 Regards.