Acid−Amide Intermolecular Hydrogen Bonding

Wash, Paul L.; Maverick, Emily F.; Chiefari, John; Lightner, David A.

doi:10.1021/ja963416e

Cited by 78 publications

(52 citation statements)

References 41 publications

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“…The parent dipyrrinone, [6]-semirubin ( 1 ) was found to obey beer’s Law, whereas its ester ( 2 ) diverges 8. Just as dipyrrinones 2 , 3 and 7 (but not 1 ) diverge from ideality with increasing concentration in CHCl 3 ,7 so do their thiolactam analogs 5 , 6 , and 8 — as might be expected. What was not originally expected was that 4 , like 1 , would not diverge; yet, its Beer’s Law behavior, like that of 8 , is found to be consistent with dimer formation.…”

Section: Resultsmentioning

confidence: 68%

“…of Lawesson’s reagent for 2 h. Under similar reaction conditions, the known methyl xanthobilirubinate ( 7 )17 was converted smoothly to the thioamide analog ( 5 ) in 83% yield. Synthesis of 4 and 8 (Scheme 1) required the known [6]-semirubin ( 1 )7 and its methyl ester ( 7 ),7 both obtained following Friedel-Crafts acylation at carbon-9 of 2,3,7,8-tetramethyl-10 H -dipyrrinone 8. Unlike the formation of thiolactam 5 from 7 , conversion of the amide of [6]-semirubin methyl ester ( 2 ) to its thioamide ( 8 ) with Lawesson’s reagent proceeded inefficiently (32% yield).…”

Section: Resultsmentioning

confidence: 99%

“…There, nature designed a molecule whose lipophilic character and poor aqueous solubility (K sp ~4 × 10 -15 M at 37°C)5 may be understood by considering the pigment’s structure in which both propionic acids are tucked inward and firmly intramolecularly hydrogen-bonded to the opposing dipyrrinones,2,3,6 the key factor in bilirubin’s aqueous solubility and metabolism. In further illustration of this attraction, strong, selective intermolecular hydrogen bonding between a carboxylic acid and a pyridone lactam has also been reported,7 to the exclusion of carboxylic acid-carboxylic acid and amide-amide hydrogen bonding. The unusual type of hydrogen bonding seen in bilirubin is probably facilitated by the adjacency of the pyrrole hydrogen and has been replicated in simpler analogs such as [6]-semirubin (Fig.…”

Section: Introductionmentioning

confidence: 97%

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Carboxylic acid to thioamide hydrogen bonding

Datta¹,

Lightner²

2009

Tetrahedron

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The lactam groups of dipyrrinones avidly engage in amide-amide hydrogen bonding to form dimeric association complexes in nonpolar solvents (in CHCl 3 , K D ~25,000 M -1 at 22°C). The corresponding thioamides (dipyrrinthiones), prepared from dipyrrinones by reaction with Lawesson's reagent, also form intermolecularly hydrogen-bonded dimers in nonpolar solvents, albeit with much weaker association constants (in CHCl 3 , K D ~200 M -1 at 22°C). When a carboxylic acid group is tethered to C(9) of the dipyrrinone, as in the hexanoic acid of [6]-semirubin, tight intramolecular hydrogen bonding between the carboxylic acid group and the lactam moiety (intramolecular K assoc ≫25,000) is found in CHCl 3 with no evidence of dimers. In contrast, the analogous dipyrrinthione, [6]-thiosemirubin, eschews intramolecular hydrogen bonds, as determined using NMR spectroscopy and vapor pressure osmometry, preferring to form intermolecularly hydrogen-bonded dimers of the thioamide-thioamide type.

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Section: Resultsmentioning

confidence: 68%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

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Carboxylic acid to thioamide hydrogen bonding

Datta¹,

Lightner²

2009

Tetrahedron

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“…6,8 This view has been challenged recently as more and more strong and unconventional hydrogen bonds have been recognized. [9][10][11][12] As a matter of fact, several types of strong hydrogen bonds have been investigated, for example, charge assisted hydrogen bonds (CAHBs), 12,13 low barrier hydrogen bonds (LBHBs), 14,15 dihydrogen bonds (DHBs), 8,16 and resonance-assisted hydrogen bonds (RAHBs). [10][11][12] In a CAHB, a positive or negative charge on the proton donating or accepting group remarkably increases the strength of the hydrogen bond.…”

Section: Introductionmentioning

confidence: 99%

How resonance assists hydrogen bonding interactions: An energy decomposition analysis

Beck

2006

J Comput Chem

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Block-localized wave function (BLW) method, which is a variant of the ab initio valence bond (VB) theory, was employed to explore the nature of resonance-assisted hydrogen bonds (RAHBs) and to investigate the mechanism of synergistic interplay between delocalization and hydrogen-bonding interactions. We examined the dimers of formic acid, formamide, 4-pyrimidinone, 2-pyridinone, 2-hydroxpyridine, and 2-hydroxycyclopenta-2,4-dien-1-one. In addition, we studied the interactions in -diketone enols with a simplified model, namely the hydrogen bonds of 3-hydroxypropenal with both ethenol and formaldehyde. The intermolecular interaction energies, either with or without the involvement of resonance, were decomposed into the Hitler-London energy (DE HL ), polarization energy (DE pol ), charge transfer energy (DE CT ), and electron correlation energy (DE cor ) terms. This allows for the examination of the character of hydrogen bonds and the impact of conjugation on hydrogen bonding interactions. Although it has been proposed that resonance-assisted hydrogen bonds are accompanied with an increasing of covalency character, our analyses showed that the enhanced interactions mostly originate from the classical dipoledipole (i.e., electrostatic) attraction, as resonance redistributes the electron density and increases the dipole moments in monomers. The covalency of hydrogen bonds, however, changes very little. This disputes the belief that RAHB is primarily covalent in nature. Accordingly, we recommend the term ''resonance-assisted binding (RAB)'' instead of ''resonance-assisted hydrogen bonding (RHAB)'' to highlight the electrostatic, which is a long-range effect, rather than the electron transfer nature of the enhanced stabilization in RAHBs.

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“…Ž Formic acid HCOOH and acetic acid CH - 3 . COOH are the two lowest members of the alkanoic acid homologous series.…”

Section: Introductionmentioning

confidence: 99%