ISSN:
1434-4475
Keywords:
2-Hydroxybenzamides
;
2-Hydroxythiobenzamides
;
Hydrogen bonds
;
Hydrogen-bond geometries
;
Ir spectra
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Description / Table of Contents:
Zusammenfassung Aus einer Zusammenstellung von spektroskopischen und strukturellen Daten von sechs entsprechenden 2-Hydroxybenzamiden und 2-Hydroxythiobenzamiden (Amid, N-Methylamid, N,N-Dimethylamid, Piperidid, Morpholid, 2,6-Dimethylpiperidid) ergeben sich bemerkenswerte Analogien zwischen O(N)-H ... O und O(N)-H ... S H-Brücken, die sowohl die H-Brücken-Muster als auch die H-Brücken-Stärken betreffen. In verdünnter Lösung sind die OH-Gruppen aller Verbindungen intramolekular mit den O(S)-Atomen der (Thio)Carbonylgruppen assoziiert, wobei die H-Brücken bei den primären und sekundären Amiden [ $$\bar v$$ (O-H)=2950−3020 cm−1, δ(OH)=12.16−11.99 ppm] und Thioamiden [ $$\bar v$$ (O-H)=2960−3060 cm−1, δ(OH)=11.65−11.13 ppm] deutlich stärker sind, als bei den tertiären Amiden [ $$\bar v$$ (O-H)=3200−3250 cm−1, δ(OH)=9.95−8.95 ppm] und Thioamiden [ $$\bar v$$ (O-H)=3245−3330 cm−1, δ(OH)=8.09−7.06 ppm]. Im Festkörper weisen die primären und sekundären (Thio)Amide ebenfalls sehr starke intramolekulare O-H ... O=C [O ... O=2.51 Å, $$\bar v$$ (O-H)=2700−2750 cm−1] und O-H ... S=C [O ... S=2.90−2.94 Å, $$\bar v$$ (O-H)=2700−2840 cm−1] H-Brücken auf; dietrans-NH-Gruppen der primären (Thio)Amide und die NH-Gruppen der sekundären (Thio)Amide verknüpfen die Moleküle über N-H ... O-H H-Brücken [N ... O=2.93−3.10 Å, $$\bar v$$ (N-H)=3318−3407 cm−1] zu Ketten; die verbleibendencis-NH-Gruppen der primären (Thio)Amide bilden zyklische, über N-H ... O=C [N ... O=2.93 Å, $$\bar v$$ (N-H)=3226 cm−1] und N-H ... S=C [N ... S=3.46−3.47 Å, $$\bar v$$ (N-H)=3233−3277 cm−1] H-Brücken gebundene, 8-Ring-Dimere. Im Gegensatz dazu sind die OH-Gruppen der tertiären (Thio)Amide im Festkörper intermolekular assoziiert und verknüpfen die Moleküle über O-H ... O=C [O ... O=2.63−2.75 Å, $$\bar v$$ (O-H)=3075−3135 cm−1] und O-H ... S=C [O ... S=3.18−3.26 Å, $$\bar v$$ (O-H)=3130−3190 cm−1] H-Brücken zu Ketten.
Notes:
Summary From a survey of spectroscopic and structural data of six corresponding 2-hydroxybenzamides and 2-hydroxythiobenzamides (amide, N-methylamide, N,N-dimethylamide, piperidide, morpholide, 2,6-dimethylpiperidide) remarkable similarities between O(N)-H ... O and O(N)-H ... S hydrogen-bonds are obtained, concerning both, hydrogen-bond patterns and hydrogen-bond strengths. In dilute solution the OH groups of all compounds are intramolecularly associated to the (thio)carbonyl O (S) atoms with distinctly larger hydrogen-bond strengths for primary and secondary amides [ $$\bar v$$ (O-H)=2950−3020 cm−1, δ(OH)=12.16−11.99 ppm] and thioamides [ $$\bar v$$ (O-H)=2960−3000 cm−1, δ(OH)=11.65−11.13 ppm], than for tertiary amides [ $$\bar v$$ (O-H)=3200−3250 cm−1, δ(OH)=9.95−8.95 ppm] and thioamides [ $$\bar v$$ (O-H)=3245−3330 cm−1, δ(OH)=8.09−7.06 ppm]. In the solid state, the OH groups of the primary and secondary (thio)amides are also engaged in rather strong intramolecular O-H ... O=C [O ... O=2.51 Å, $$\bar v$$ (O-H)=2700−2750 cm−1] and O-H ... S=C [O ... S=2.90−2.94 Å, $$\bar v$$ (O-H)=2700−2840 cm−1] hydrogen-bonds; thetrans-NH groups of the primary (thio)amides and the NH groups of the secondary (thio)amides connect the molecules to N-H ... O-H [N ... O=2.93−3.10 Å, $$\bar v$$ (N-H)=3319−3407 cm−1] hydrogen-bonded chains; the remainingcis-NH groups of the primary (thio)amides give rise to eight-membered cyclic dimers via N-H ... O=C [N ... O=2.93 Å, $$\bar v$$ (N-H)=3226 cm−1] and N-H ... S=C [N ... S=3.46−3.47 Å, $$\bar v$$ (N-H)=3233−3277 cm−1] hydrogen-bonds. Contrary, the OH groups of the tertiary (thio)amides are intermolecular associated in the solid state and link the molecules to O-H ... O=C [O ... O=2.63−2.75 Å, $$\bar v$$ (O-H)=3075−3135 cm−1] and O-H ... S=C [O ... S=3.18−3.26 Å, $$\bar v$$ (O-H)=3130−3190 cm−1] hydrogen-bonded chains.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00808374
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