The Physical Properties of Some Triazo Compounds. II. Dipole Moments<sup>1</sup>

Spauschus, H. O.; Scott, John M.

doi:10.1021/ja01145a071

Cited by 13 publications

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“…(Phenylimino)tris(dimethylamino)phosphazene 5 was synthesized according to the procedure described in ref 5. The same procedure was employed for synthesis of (2-chlorophenylimino)tris(dimethylamino)phosphorane 11 (starting compounds: 2-Cl-C 6H4-N3 27,28 and (Me2N)3P (Fluka)). The crude product (a brown oil) was distilled to give a yellowish oil (yield 65%, bp 137 °C (0.15 Torr)).…”

Section: Methodsmentioning

confidence: 99%

Self-Consistent Spectrophotometric Basicity Scale in Acetonitrile Covering the Range between Pyridine and DBU

et al. 2000

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A self-consistent spectrophotometric basicity scale in acetonitrile, including DBU, ten (arylimino)tris(1-pyrrolidinyl)phosphoranes, two (arylimino)tris(dimethylamino)phosphoranes, 2-phenyl-1,1,3, 3-tetramethylguanidine, 1-(2-tolyl)biguanide, benzylamine, two substituted benzimidazoles, pyridine, and ten substituted pyridines, has been created. The span of the scale is almost 12 pK(a) units. Altogether, 29 different bases were studied and 53 independent equilibrium constant measurements were carried out, each describing the relative basicity of two bases. The scale is anchored to the pK(a) value of pyridine of 12.33 that has been measured by Coetzee et al. Comparison of the basicity data of phenyliminophosphoranes and phenyltetramethylguanidines implies that the P=N bond in the (arylimino)tris(1-pyrrolidinyl)phosphoranes involves contribution from the ylidic (zwitterionic) structure analogous to that found in phosphorus ylides.

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Section: Methodsmentioning

confidence: 99%

Self-Consistent Spectrophotometric Basicity Scale in Acetonitrile Covering the Range between Pyridine and DBU

et al. 2000

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“…Certain -azido carbonyl compounds have long been known to be unstable substances. -Azidoacetaldehyde could not be purified (152), while a-azidoacetone has been reported to decompose upon storage in the refrigerator (366). A strong odor of benzaldehyde and a negative test for an azido group by testing for decomposition in sulfuric acid was characteristic of the material resulting from the storage of desyl azide for several months at room temperature (52).…”

Section: Oh-mentioning

confidence: 99%

Alkyl and Aryl Azides.

Boyer¹,

Canter²

1954

Chem. Rev.

217

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General and theoretical aspects

Treinin

1971

PATAI'S Chemistry of Functional Groups

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Orbitals . 1. Slater-type atomic orbitals 2. Gaussian lobe functions representation G. Other than LCAO Methods . H. Conclusion . IV. REFERENCES . . . F. LCAO Self-consistent Field (Hartrec-Fock) Molecular . 44 45 45 47 48 48 50 50 52 52 c For discussion of the elFcctive radius of Ns7 in crystals see scction 1I.A.f For discussion of the chargc-transfer-to-solvent spectrum of h'c scc scction 1I.G. 9 The electroncgativity of N, is bctwecn that of Br a n d I (2.5). Thc h~lulliken scale is used herea. h En = E" + 2.60, where Eo is the clcctrodc potential; scc J. 0. Edwards, J. Am. Chcnr. SOL, 76, 1540 (1954). 4A. Treinin also capable of conjugation through their non-bonding electrons and thus can act as electron-donors, i.e. they exert a positive resonance efect ( -I-R). When this m-interaction is strong the pseudohalide group may become colinear with the atom to which it is bound6. This resonance effect is responsible for the effect of the azido group on a benzene ring, its ortho-para orienting character and its activating influence on electrophilic substitutbn. A significant difference between halides and pseudohalides lies in the 'unsaturation' of the latter; they contain low-lying, unfilled 7r orbitals which can accept electrons. This puts them higher than halides in the spectrochemical seriesfo.The reducing power of the halide and pseudohalide ions increases in the following orderff: F-, NCO-, C1-, Ng, Br-, SCN-, I-. In this and other respects the azido group shows close resemb!ance to bromine ( Table 1). The data recorded in Table 1 describe the behaviour of the azido group in its equilibrium nuclear configuration. However the main interest in this group lies in those properties which depend on changes in its geometry, its bending to form cyclic compounds7 and its dissociation to -N +N,. Obviously this has no parallel in the halogen series. B. Electronic Structure (Simplified Model)The general shape of covalent azides is shown in Figure 1. X I t L FIGURE I . The geometry of covalent azidcs (L is the atom to which N, is bound; all the nuclei lie in the xz plane).As late as 1944 azides were considered to have the classical structure RN=NdV, namely with pentavalent nitrogen ,l. This picture has been completely abandoned as it is now generally accepted that nitro-1. General and theoretical aspects 5 gen obeys the octet rule. keeping with the octet rule and the ' adjacent charge rule' 22 : One can write two canonical structures in Resonance of I and 11, with equal contributions, leads to bond order 1.5 and 2-5 for the bonds N,-N, and Nb-N, respectively, in agreement with the values derived from force constants (section 1I.E). The formal charges on N,, Nb and N, corresponding to the resonance hybrid 1-11 are -0.5, + 1 and -0-5 respectively. In both structures * For a recent discussion of hybridization and valence states of nitrogen see reference 27. General and theoretical aspects* Not to be confused with 'self-consistcnt-ficld'. t In this case the total energy of the T system is smaller than the sum of the orbital en...

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The Physical Properties of Some Triazo Compounds. II. Dipole Moments¹

Cited by 13 publications

References 0 publications

Self-Consistent Spectrophotometric Basicity Scale in Acetonitrile Covering the Range between Pyridine and DBU

Self-Consistent Spectrophotometric Basicity Scale in Acetonitrile Covering the Range between Pyridine and DBU

Alkyl and Aryl Azides.

General and theoretical aspects

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The Physical Properties of Some Triazo Compounds. II. Dipole Moments1

Cited by 13 publications

References 0 publications

Self-Consistent Spectrophotometric Basicity Scale in Acetonitrile Covering the Range between Pyridine and DBU

Self-Consistent Spectrophotometric Basicity Scale in Acetonitrile Covering the Range between Pyridine and DBU

Alkyl and Aryl Azides.

General and theoretical aspects

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Product

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The Physical Properties of Some Triazo Compounds. II. Dipole Moments¹