Spectroscopic studies of chemically liberated "free" -OH groups in aqueous N2H4, NH3, and CH3NH2 solutions

Charles Angell, Dana L. Fields

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

As a contribution to understanding and identifying the nature of the disputed "broken" hydrogen bond in aqueous solutions we have sought to compare the spectroscopic character of "free" -OH groups produced by chemical means at constant temperature with that of the putative "free" -OH produced in pure water alcohols, etc. by temperature increases. "Free", or at least very weakly bonded, -OH groups have been produced quasi-stoichiometrically at room temperature by displacing bound -OH groups from OH⋯O bonds previously free with previously free -NH groups, the competitive status of which has been abruptly increased by protonation of the amine group. The sharp overtone bands of the unbonded -NH groups necessarily present in amine + H2O solutions (due to the excess of protons over lone pairs) disappear stoichiometrically on protonation using HClO4, and an equivalent number of weakly bonding -OH groups are produced. The spectroscopic signature of the chemically liberated -OH group is almost indistinguishable from that of the group liberated thermally, and a well-defined isosbestic point at 1442 nm (close to the approximate isosbestic point at 1440-1450 nm in the heated water spectra) implies that the same mechanism of "exciting across the centroid" (a (strong bond) ↔ (weak bond) exchange within a continuum model) is involved in each case.

Original languageEnglish (US)
Pages (from-to)4565-4569
Number of pages5
JournalJournal of Physical Chemistry
Volume89
Issue number21
StatePublished - 1985
Externally publishedYes

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Protonation
Amines
Water
Temperature
Protons
Hydrogen bonds
Alcohols
amines
centroids
water
alcohols
signatures
hydrogen bonds
continuums
aqueous solutions
harmonics
temperature
protons
room temperature

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Spectroscopic studies of chemically liberated "free" -OH groups in aqueous N2H4, NH3, and CH3NH2 solutions. / Angell, Charles; Fields, Dana L.

In: Journal of Physical Chemistry, Vol. 89, No. 21, 1985, p. 4565-4569.

Research output: Contribution to journalArticle

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