title: Enhanced Basicity of Push-Pull Nitrogen Bases in the Gas Phase.
abstract: Nitrogen bases containing one or more pushing amino-group(s) directly linked to a pulling cyano, imino, or phosphoimino group, as well as those in which the pushing and pulling moieties are separated by a conjugated spacer (C═X)n, where X is CH or N, display an exceptionally strong basicity. The n-π conjugation between the pushing and pulling groups in such systems lowers the basicity of the pushing amino-group(s) and increases the basicity of the pulling cyano, imino, or phosphoimino group. In the gas phase, most of the so-called push-pull nitrogen bases exhibit a very high basicity. This paper presents an analysis of the exceptional gas-phase basicity, mostly in terms of experimental data, in relation with structure and conjugation of various subfamilies of push-pull nitrogen bases: nitriles, azoles, azines, amidines, guanidines, vinamidines, biguanides, and phosphazenes. The strong basicity of biomolecules containing a push-pull nitrogen substructure, such as bioamines, amino acids, and peptides containing push-pull side chains, nucleobases, and their nucleosides and nucleotides, is also analyzed. Progress and perspectives of experimental determinations of GBs and PAs of highly basic compounds, termed as "superbases", are presented and benchmarked on the basis of theoretical calculations on existing or hypothetical molecules.
authors.affiliation: Department of Chemistry, Warsaw University of Life Sciences (SGGW) , ul. Nowoursynowska 159c, 02-776 Warszawa, Poland.
authors.forename: Ewa D
authors.initials: ED
authors.lastname: Raczyńska
authors.affiliation: Institut de Chimie de Nice (ICN) - UMR CNRS 7272, University Nice Sophia Antipolis , Parc Valrose, 06108 Nice Cedex 2, France.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Gal
authors.affiliation: Institut de Chimie de Nice (ICN) - UMR CNRS 7272, University Nice Sophia Antipolis , Parc Valrose, 06108 Nice Cedex 2, France.
authors.forename: Pierre-Charles
authors.initials: PC
authors.lastname: Maria
mesh_terms: D000468:Alkalies / Q000737:chemistry*; D000588:Amines / Q000737:chemistry; D000596:Amino Acids / Q000737:chemistry; D001393:Azoles / Q000737:chemistry; D001645:Biguanides / Q000737:chemistry; D005740:Gases / Q000737:chemistry*; D007097:Imines / Q000737:chemistry; D008024:Ligands; D015394:Molecular Structure; D009570:Nitriles / Q000737:chemistry; D009930:Organic Chemicals / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry; D017553:Phosphorus Compounds / Q000737:chemistry
chemical_list: D000468:Alkalies; D000588:Amines; D000596:Amino Acids; D001393:Azoles; D001645:Biguanides; D005740:Gases; D007097:Imines; D008024:Ligands; D009570:Nitriles; D009930:Organic Chemicals; D010455:Peptides; D017553:Phosphorus Compounds