Amino nitrogen and carbonyl oxygen in competitive situations: which is the best hydrogen-bond acceptor site?

Ziao, Nahossé; Laurence, Christian; Questel, Jean‐Yves Le

doi:10.1039/b202248f

Cited by 24 publications

(21 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Few attempts in this direction were earlier also made, to rank the effectiveness of HB groups and the quantities were referred by various names such as probabilities, relative success, propensity or competition function. [25][26][27][28][29][30] To investigate the efficacy of fluorine for making interactions, these parameters were calculated using Cambridge Structural Database (CSD) (Version 5.31). 15 All intra-molecular short-contacts were excluded.…”

Section: High Occurrence Of C-h F Interactions In Organic Moleculesmentioning

confidence: 99%

The role of weak intermolecular C–H...F interactions in supramolecular assembly: Structural investigations on 3,5- dibenzylidene-piperidin-4-one and database analysis

et al. 2011

View full text Add to dashboard Cite

The fluorinated and non-fluorinated dibenzylidene-4-piperidones were synthesized and their structures examined using X-ray crystallography. Interestingly, the para-fluorosubstituted dibenzylidene compound, in contrast to other analogs, is characterized by C-H. . . F bonded one-dimensional packing motif. To evaluate the ability of hydrogen bond donors and acceptors for forming interactions, in general and competitive situation, we have defined statistical descriptors. Analysis of Cambridge Structural Database using these newly defined parameters reveals high propensity of C-H. . . F interactions in organic crystals. The present structural study suggests much larger role of fluorine driven intermolecular interactions that are even though weak, but possess significant ability to direct and alter the packing.

show abstract

Section: High Occurrence Of C-h F Interactions In Organic Moleculesmentioning

confidence: 99%

The role of weak intermolecular C–H...F interactions in supramolecular assembly: Structural investigations on 3,5- dibenzylidene-piperidin-4-one and database analysis

et al. 2011

View full text Add to dashboard Cite

show abstract

“…It was found that the electron withdrawing group decreased the CN bond rotation which made the carbamate units as less nucleophilic. Zhao et al studied the influence of extended double bond of CN bond by alkyl substitution and concluded that the loan pair electron in the nitrogen donated to carbonyl carbon through conjugation. Shigemoto et al had done detailed theoretical calculation for binding of ester unit at the Ti‐O‐R center through RO‐C=O…Ti; O=C‐O(R)…Ti and Lewis acid in the transesterification reaction.…”

Section: Resultsmentioning

confidence: 99%

Catalysts and temperature driven melt polycondensation reaction for helical poly(ester-urethane)s based on natural L-amino acids

Anantharaj

Jayakannan

2015

J. Polym. Sci. Part A: Polym. Chem.

View full text Add to dashboard Cite

Catalyst and temperature driven melt polycondensation reaction was developed for natural L‐amino acid monomers to produce new classes of poly(ester‐urethane)s. Wide ranges of catalysts from alkali, alkali earth metal, transition metal and lanthanides were developed for the condensation of amino acid monomers with diols to yield poly(ester‐urethane)s. A‐B Diblock and A‐B‐A triblock species were obtained by carefully choosing mono‐ or diols in model reactions. More than two dozens of transition metal and lanthanide catalysts were identified for the polycondensation to yield high molecular weight poly(ester‐urethane)s. Theoretical studies revealed that the carbonyl carbon in ester possessed low electron density compared to the carbonyl carbon in urethane which driven the thermo‐selective polymerization process. Optical purity of the L‐amino acid residues in the melt polycondensation process was investigated using D‐ and L‐isomers and the resultant products were analyzed by chiral‐HPLC and CD spectroscopy. CD analysis revealed that the amino acid based polymers were self‐assembled as β‐sheet and polyproline type II secondary structures. Electron and atomic force microscopic analysis confirmed the formation of helical nano‐fibrous morphology in poly(ester‐urethane)s. The newly developed melt polycondensation process is very efficient and optimized for wide range of catalysts to produce diverse polymer structures from natural L‐amino acids. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 1065–1077

show abstract

“…For example, phenol and water can form either complex A, where phenol acts as the HBD, or B, where water serves as the HBD (Scheme 4.1). 17, 16 and 15, respectively. conjugation of the nitrogen lone pair of amino groups with electron-withdrawing groups, such as cyano or carbonyl in the push-pull compounds N T C N [43] and N T C O [44] (where T is a group transmitting the conjugation), lowers the basicity of the amino nitrogen so dramatically that the carbonyl and cyano groups are the main hydrogen-bond acceptor sites and not the amino nitrogen. In terms of Gibbs energies of complexation, it is found that A is 7.8 kJ mol −1 more stable than B.…”

Section: Structure Of Hydrogen-bonded Complexesmentioning

confidence: 99%

Thermodynamic and Spectroscopic Scales of Hydrogen‐Bond Basicity and Affinity

2009

Lewis Basicity and Affinity Scales

View full text Add to dashboard Cite

Water, alcohols, phenols, hydrogen halides, carboxylic acids, primary and secondary amines and amides, thiols, 1-alkynes and so on constitute a special class of Lewis acids. They all contain an XH group in which the hydrogen atom is bonded to an electronegative atom X and bears a partial positive charge. Therefore, the hydrogen is attracted, by means of electrostatic forces, toward high electron density regions, mainly the lone pairs of Lewis bases B, and a hydrogen bond (HB) X H · · · B is formed. In addition to this electrostatic interaction, there is a charge transfer from the base to the antibonding orbital σ * of the X H sigma bond. The respective contributions of electrostatic forces and charge transfer are a matter of debate. A modern electrostatic model of the hydrogen bond provides a near-quantitative description of structure and properties for a wide range of typical hydrogen bonds [1]. In contrast, NBO analysis suggests that charge transfer of n→σ * type is a characteristic feature of hydrogen bonding [2,3]. In any case, the existence of even a small charge transfer allows the hydrogen-bonding interaction to be considered as Lewis acid/base in nature [4]. The hydrogen-bond donor (HBD) XH is the electron acceptor and the hydrogen-bond acceptor (HBA) B is the electron donor. In the HSAB concept, HBDs are classified as hard Lewis acids [4] from the simple observation that the hydrogen bond is stronger when B is fluorine, oxygen or nitrogen than when it is iodine, sulfur or phosphorus, respectively.The reaction 4.1 of formation of a hydrogen bond between the molecules XH and B:can be used for the construction of a Lewis basicity scale, if a reference HBD is chosen and if the equilibrium constant K of the reaction is measured for a series of bases B under the same conditions: physical state (gas or solution in a given solvent), temperature and pressure. Such a scale, as logK or ∆G, must be named a hydrogen-bond basicity scale.

show abstract

Amino nitrogen and carbonyl oxygen in competitive situations: which is the best hydrogen-bond acceptor site?

Cited by 24 publications

References 38 publications

The role of weak intermolecular C–H...F interactions in supramolecular assembly: Structural investigations on 3,5- dibenzylidene-piperidin-4-one and database analysis

The role of weak intermolecular C–H...F interactions in supramolecular assembly: Structural investigations on 3,5- dibenzylidene-piperidin-4-one and database analysis

Catalysts and temperature driven melt polycondensation reaction for helical poly(ester-urethane)s based on natural L-amino acids

Thermodynamic and Spectroscopic Scales of Hydrogen‐Bond Basicity and Affinity

Contact Info

Product

Resources

About