Extremely strong but sluggish amine bases

Alder, Roger W.; Goode, Nigel C.; Miller, Nigel; Hibbert, Frank; Hunte, Kenneth P. P.; Robbins, Heather J.

doi:10.1039/c39780000089

Cited by 49 publications

(27 citation statements)

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“…Table 1 shows the pK, values for some substituted 1,8-diaminonaphthalenes. While increasing N-methylation of 3 results in the case of the bis(methy1amino) compound 5 and even in the N,N,N'-trimethyl derivative 6 in only a small increase in basicity (this being mainly the result of inductive effects), the introduction of the fourth N-methyl group to give 4 causes a sudden increase in basicity by nearly six powers of ten. The way in which the basicity increases with increasing N-methylation of 2 suggests that steric effects play a very important role.…”

Section: Introductionmentioning

confidence: 96%

“Proton Sponges” and the Geometry of Hydrogen Bonds: Aromatic Nitrogen Bases with Exceptional Basicities

Staab

Saupe

1988

Angew. Chem. Int. Ed. Engl.

369

185

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Certain aromatic diamines (the "proton sponges") are found to have exceptionally high basicity constants: this is due to spatial interaction of the basic centers, which are in close proximity. The two factors which are most important in causing this effect are, on the one hand, the extreme steric strain in these systems and the destabilizing effect of the overlap of the nitrogen lone pairs of the neutral diamines and, on the other, the strong N . . H . . . N hydrogen bonds which are formed on monoprotonation and which lead to a considerable relaxation of the steric strain. By the systematic variation of the structures of such aromatic diamines we have been able to study these effects as a function of steric factors, in particular of the geometry and the bond length of the N -. . H . . -N hydrogen bonds, by means of X-ray structural analysis. The hydrophobic shielding of the basic centers and the N . . . H . . . N hydrogen bonds, which was characteristic of the "proton sponge" compounds studied previously, is indeed responsible for the extremely low rate of protonation and deprotonation of these compounds; however, it apparently has no influence on their high thermodynamic basicity. The recent synthesis and basicity determination of a new type of "proton sponge" with no hydrophobic shielding whatever show that not only very strong but also kinetically active bases are accessible using the "proton sponge" concept. Their unusual properties, which are discussed here as the result of steric interactions between two basic centers, provide examples of the fact that cooperative steric interactions of reactive structural elements can lead to properties which cannot be derived from an isolated consideration of the various functional groups. Such "proximity effects" are certainly of general importance in chemistry and biochemistry; the study of their structure-function relationships is worthy of closer consideration.

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Section: Introductionmentioning

confidence: 96%

“Proton Sponges” and the Geometry of Hydrogen Bonds: Aromatic Nitrogen Bases with Exceptional Basicities

Staab

Saupe

1988

Angew. Chem. Int. Ed. Engl.

369

185

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“…The NHN hydrogen bonds in homoconjugated nitrogen bases play an important role in so-called proton sponges (Alder, Bowman, Steele & Wintermann, 1968;Hibbert, 1974;de Groot & Sikkema, 1976;Awwal & Hibbert, 1977;Alder, Goode, Miller, Hibbert, Hunte & Robbins, 1978;Glowiak, Malarski, Sobczyk & Grech, 1987). Among the NHN systems the bi-centre bases with 1,8-bis(dimethylamino)naphthalene (DMAN) as a representative proton sponge are of particular interest.…”

Section: Institute Of Fundamental Chemistry Technical University Ofmentioning

confidence: 99%

Structure of 8-dimethylamino-1-dimethylammonionaphthalene hydrogen squarate

Kanters¹,

Schouten²,

Kroon³

et al. 1991

Acta Crystallogr C

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“…With mineral or organic acids DMAN forms very strong ionic complexes with intramolecular [N...H...N] hydrogen bonds. These bonds play an important role in the understanding of the proton sponges properties [3,4,5]. Among the NHN systems the bi-centre bases with 1,8-bis(dimethylamino)naphthalene as a representative proton sponge, have attracted considerable interest.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and X-ray crystal structure investigations of the complexes of a proton sponge with selected inorganic acids: Crystal structure of DMAN.HI complex

Łasocha¹,

Rafalska-Łasocha²

2006

Cryst. Res. Technol.

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A series of ionic complexes of 1,8 -bis(dimethylamino)naphthalene with selected inorganic acids such as HCl, HBr, HI, HSCN and HBF 4 were synthesised and thoroughly investigated by means of powder diffractometry and analytical methods. The crystallographic data for these compounds as well as the results of the structure solution by powder diffraction methods of the 1,8 -bis(dimethylamino)naphthalene.HI complex, which crystallizes in the monoclinic system, S.G. P2 1 /c (14), a=7.999(2)Å, b=23.053(3)Å, c=7.948(1)Å, β=99.63°, R F =17.1%, R wp =15.5%, are discussed and presented in this work.

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Extremely strong but sluggish amine bases

Cited by 49 publications

References 0 publications

“Proton Sponges” and the Geometry of Hydrogen Bonds: Aromatic Nitrogen Bases with Exceptional Basicities

“Proton Sponges” and the Geometry of Hydrogen Bonds: Aromatic Nitrogen Bases with Exceptional Basicities

Structure of 8-dimethylamino-1-dimethylammonionaphthalene hydrogen squarate

Synthesis and X-ray crystal structure investigations of the complexes of a proton sponge with selected inorganic acids: Crystal structure of DMAN.HI complex

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