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  • Measuring the relative hydrogen-bonding strengths of alcohols in aprotic organic solvents.

Measuring the relative hydrogen-bonding strengths of alcohols in aprotic organic solvents.

Chemphyschem : a European journal of chemical physics and physical chemistry (2014-11-25)
Malcolm E Tessensohn, Melvyn Lee, Hajime Hirao, Richard D Webster
ABSTRACT

Voltammetric experiments with 9,10-anthraquinone and 1,4-benzoquinone performed under controlled moisture conditions indicate that the hydrogen-bond strengths of alcohols in aprotic organic solvents can be differentiated by the electrochemical parameter ΔEp (red) =|Ep (red(1)) -Ep (red(2)) |, which is the potential separation between the two one-electron reduction processes. This electrochemical parameter is inversely related to the strength of the interactions and can be used to differentiate between primary, secondary, tertiary alcohols, and even diols, as it is sensitive to both their steric and electronic properties. The results are highly reproducible across two solvents with substantially different hydrogen-bonding properties (CH3 CN and CH2 Cl2 ) and are supported by density functional theory calculations. This indicates that the numerous solvent-alcohol interactions are less significant than the quinone-alcohol hydrogen-bonding interactions. The utility of ΔEp (red) was illustrated by comparisons between 1) 3,3,3-trifluoro-n-propanol and 1,3-difluoroisopropanol and 2) ethylene glycol and 2,2,2-trifluoroethanol.

MATERIALS
Product Number
Brand
Product Description

Supelco
Ethylene glycol, Pharmaceutical Secondary Standard; Certified Reference Material
Supelco
Ethylene glycol solution, NMR reference standard, 80% in DMSO-d6 (99.9 atom % D), NMR tube size 5 mm × 8 in.
Sigma-Aldrich
3,3,3-trifluoro-1-propanol, AldrichCPR
USP
1,4-Benzoquinone, United States Pharmacopeia (USP) Reference Standard
USP
Dehydrated Alcohol, United States Pharmacopeia (USP) Reference Standard
Sigma-Aldrich
2-Butanol, anhydrous, 99.5%
Sigma-Aldrich
Methanol, anhydrous, 99.8%
Sigma-Aldrich
2-Methyl-1-propanol, anhydrous, 99.5%
Supelco
Ethanol solution, certified reference material, 2000 μg/mL in methanol
Sigma-Aldrich
2-Methyl-1-propanol, BioUltra, for molecular biology, ≥99.5% (GC)
Supelco
2,2,2-Trifluoroethanol, analytical standard, for NMR spectroscopy
Supelco
2-Butanol, analytical standard
Supelco
1-Butanol, analytical standard
Sigma-Aldrich
Ethylene glycol, BioUltra, ≥99.5% (GC)
Supelco
2-Methyl-1-propanol, analytical standard
Supelco
Methanol, analytical standard
Sigma-Aldrich
Anthraquinone, 97%
Sigma-Aldrich
1-Butanol, anhydrous, 99.8%
Sigma-Aldrich
1-Butanol, for molecular biology, ≥99%
Supelco
1-Butanol, Pharmaceutical Secondary Standard; Certified Reference Material
Sigma-Aldrich
p-Benzoquinone, reagent grade, ≥98%
USP
Ethylene glycol, United States Pharmacopeia (USP) Reference Standard
Sigma-Aldrich
2-Methyl-1-propanol, suitable for HPLC, 99.5%
Sigma-Aldrich
Methanol, BioReagent, ≥99.93%
Sigma-Aldrich
Methanol, NMR reference standard
Supelco
Melting point standard 283-286°C, analytical standard
Sigma-Aldrich
Isopropyl alcohol, ≥99.7%, FCC, FG
Sigma-Aldrich
Ethylene glycol, anhydrous, 99.8%
Supelco
Dehydrated Alcohol, Pharmaceutical Secondary Standard; Certified Reference Material
Supelco
1,4-Benzoquinone, Pharmaceutical Secondary Standard; Certified Reference Material