Structure and behavior of organic analytical reagents VI. Heats and entropies of formation of several divalent metal chelates of 2- and 4-methyl-8-hydroxyquinoline

Johnston, W. D.; Freiser, H.

doi:10.1016/s0003-2670(00)87719-3

Structure and behavior of organic analytical reagents VI. Heats and entropies of formation of several divalent metal chelates of 2- and 4-methyl-8-hydroxyquinoline

Journal Article · Fri Jan 01 00:00:00 EST 1954 · Analytica Chimica Acta

DOI:https://doi.org/10.1016/s0003-2670(00)87719-3· OSTI ID:4410327

Johnston, W. D. ^[1]; Freiser, H. ^[1]

Univ. of Pittsburgh, PA (United States)

The Calvin-Bjerrum titration technique for the determination of chelate formation constants has been applied to the Cu(II), Ni(II), Co(II), Zn(II) and Mn(II) chelates of 2- and 4-methyl-8-hydroxyquinoline. Measurements were made at several temperatures in order to evaluate ΔH and ΔS values of chelation. The results obtained were interpreted in terms of steric hindrance of the 2-methyl group. In all cases the heats of formation of the chelates of 2-methyl-8-hydroxyquinoline were remarkably more positive than those for the corresponding chelates of 4-methyl-8-hydroxyquinoline. This large difference in the strengths of the metal-chelate bonds is apparently due to the hindrance of the methyl groups which prevent the close grouping of the two reagent molecules around the metal in chelates of 2-methyl-8-hydroxyquinoline. The lower bond strength in chelates of 2-methyl-8-hydroxy-quinoline is partially compensated by a relatively larger entropy of formation. This is attributed to decreased solvent chelate interaction caused by the shielding of the polar O, N, and metal atoms by the 2-methyl groups. Finally, the determination of chelate formation constants of 2-phenyl-8-hydroxyqumoline has been carried out to further extend our study of steric effects in metal chelates.

Research Organization:: Univ. of Pittsburgh, PA (United States)

Sponsoring Organization:: US Atomic Energy Commission (AEC)

NSA Number:: NSA-07-005712

OSTI ID:: 4410327

Report Number(s):: NYO--3772

Journal Information:: Analytica Chimica Acta, Journal Name: Analytica Chimica Acta Vol. 11; ISSN 0003-2670

Publisher:: ElsevierCopyright Statement

Country of Publication:: United States

Language:: English

References (12)

Structure and behavior of organic analytical reagents Charles, Robert G.; Freiser, Henry Analytica Chimica Acta, Vol. 11 https://doi.org/10.1016/S0003-2670(00)87683-7	journal	January 1954
Structure and behavior of organic analytical reagents Charles, Robert G.; Freiser, Henry Analytica Chimica Acta, Vol. 11 https://doi.org/10.1016/S0003-2670(00)87703-X	journal	January 1954
Inorganic Complex Compounds Containing Polydentate Groups. VI. Formation Constants of Complex Ions of Diethylenetriamine and Triethylenetetramine with Divalent Ions Jonassen, Hans B.; Hurst, G. G.; LeBlanc, R. B. The Journal of Physical Chemistry, Vol. 56, Issue 1 https://doi.org/10.1021/j150493a004	journal	January 1952
Thermodynamics of Chelation. I. The Statistical Factor in Chelate Ring Formation¹ Spike, Clark G.; Parry, Robert W. Journal of the American Chemical Society, Vol. 75, Issue 11 https://doi.org/10.1021/ja01107a053	journal	June 1953
Structure and Behavior of Organic Analytical Reagents. I. The Calvin—Bjerrum Method for Determination of Chelate Stability Freiser, Henry; Charles, Robert G.; Johnston, W. Dwight Journal of the American Chemical Society, Vol. 74, Issue 6 https://doi.org/10.1021/ja01126a006	journal	March 1952
Structure and Behavior of Organic Analytical Reagents. II. Stability of Chelates of o-Aminophenol and of o-Aminobenzenethiol¹ Charles, Robert G.; Freiser, Henry Journal of the American Chemical Society, Vol. 74, Issue 6 https://doi.org/10.1021/ja01126a007	journal	March 1952
Structure and Behavior of Organic Analytical Reagents. III. Stability of Chelates of 8-Hydroxyquinoline and Analogous Reagents ¹ Johnston, William Dwight; Freiser, Henry Journal of the American Chemical Society, Vol. 74, Issue 21 https://doi.org/10.1021/ja01141a001	journal	November 1952
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Structure and behavior of organic analytical reagents VI. Heats and entropies of formation of several divalent metal chelates of 2- and 4-methyl-8-hydroxyquinoline

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