NMR Spectroscopic and X-Ray Structural Studies of Two Diazadiphosphetidines

The crystal structures of the two diazadiphosphetidines, [PhNP(OCH2CF3)]2 (1) and [MeNP(NMe2)(O2C6H4)]2 (2) have been determined. The trifluoroethoxy groups in (1) have a trans orientation. The phosphorus chemical shift for (1) is at 189.8 δ. On standing in solution, (1) transforms slowly (∼ 10 days) and almost completely into its 'high-field' (cis) isomer (142.2δ).

A PPP AND CNDO Study of Dithiocarbonic Antonic Derivatives

The application of the CNDO and PPP-CI methods to N,N-dimethyl dithiocarbamate, O-methyl dithiocarbonate (methyl xanthate) and methyl trithiocarbonate ions for the elucidation of electronic structure and electronic spectra is described. The CNDO/2 calculations have been used to obtain the one centre core integrals of the ionic compounds required in calculating the pi electronic spectra of these molecules using the PPP method. The calculated spectra are in good agreement with the experiment. The atomic charge densities determined for alkyl xanthate, dithiocarbamate and trithiocarbonate ions support the earlier qualitative predictions regarding electronic structure from spectroscopic and other studies.

Kinetics Of The Aminolysis Reactions Of Chlorocyclotriphosphazenes-Changeover From A Sn2(P) To A Sn1(P) Mechanism

A change-over from SN2(P) to SN1(P) mechanism is established for the chlorine replacement reactions of halogenocyclophosphazenes; this mechanistic change-over helps in rationalising the diverse findings reported for this class of reactions.

Electronic Structure of some Substituted azolidines.CNDO/2, NMR and vibratational spectoroscopic studies

The 1H and 13C chemical shifts, characteristic vibrational frequencies and force constants for some substituted azolidines are correlated with the results of the CNDO/2 calculations. The influence of the exo and endo heteroatoms on the electronic structure of the heterocyclic ring are discussed.

Conformation And C-N Rotational Barrier Of Dithiocarbamate Esters Nmr And Molecular-Orbital Studies

The variable temperature proton and ambient temperature carbon-13 NMR spectra of S-methyl dithiocarbamate esters have been recorded. The results of the theoretical energy calculations (CNDO/2 and EHT types) together with the experimental data have been interpreted in terms of the molecular conformations. The barrier heights for the rotation about the thioamide C—N bond are calculated using the CNDO/2 method and the results are discussed in terms of the computed charge densities and bond orders.

Bicyclic Phosphazenes Derived from (Amino) Cyclotetraphosphazenes

Amination reactions of 2,6-bis(primary amino)cyclotetraphosphazenes yield not only the expected (amino)cyclotetraphosphazenes but also novel trans-annular bridged bicyclic phosphazenes by an intramolecular substitution pathway. In addition, resins are formed in some reactions by an intermolecular condensation. The effect of substituents attached to the phosphazene ring, the attacking nucleophile and solvent on the formation of the trans-annular P-N-P bridge is considered in detail in relation to plausible reaction mechanisms. Analytical separation of bicyclic phosphazenes by high performance liquid chromatography (HPLC) on a reverse phase silica column is demonstrated. Structural features of bicyclic phosphazenes and salient aspects of their NVR spectroscopic data are discussed.

Synthesis of Diversified Thioethers,1-Aroylalkylisoquinolin-1-yl Thioethers, by Electrophilic S-Alkylation of 3-Phenyl Isoquinoline-1(2H)-thione

A mild and efficient method for the synthesis of thioethers has been developed. The 3-phenylisoquinoline-1(2H)-thione underwent S-alkylation to afford structurally diverse sulfides in high yield.

The 31p nmr Spectra of Isomeric Diaminohexa-hlorocyclotetraphosphazatetraenes; Examples of a2b2 and aa'bb' spin Systems

The 31P nmr spectra of 2,4- and 2,6-diamino-derivatives of octachlorocyclotetraphosphazatetraene, N4P4Cl6(NR1R2)2 (R1 = H, R2 = But; R1 = H, R2 = CH2Ph; R1 = Me, R2 = Ph), have been measured. The 2,4- and 2,6-isomers were analysed as AA'BB' and A2B2 spin systems respectively. In the 2,4-isomers the spin-spin couplings 2J(PNP) and 4J(PNPNP) were of opposite sign.

Reaction of Thiophosphoryl Fluoride and Thiophosphoryl Chloride with Dimethyl Sulphoxide

Solid complexes of thiophosphoryl fluoride and thiophosphoryl chloride with dimethyl sulphoxide (DMSO) have been prepared and characterized.

The Reaction of N4P4Cl8 with Dibenzylamine: Formation of an Unusual Bicyclic Phosphazene, N4P4[N(CH2Ph)2]6(NCH2Ph), by Dealkylation

The reactions of halogenocyclotetraphosphazatetraenes N4P4X8, with nucleophiles have received little attention and only the reactions of the octachloride, N4P4Cl8, with amines have been investigated in any detail.1 Millington and Sowerby2 studied the reaction of N4P4Cl8 with dimethylamine and isolated the derivatives, N4P4Cl8-n (NMe2)n, n = 2,3,4,5,6,8;several N-methylanilino derivatives

A Convenient High-Yield Room-Temerature Synthesis of Mixed Tri(Amino) Silanes by Transmination of Tris(Dicyclohexylamino) Silane And-Their Characterization

Tris(dicyclohexylamino)silane. (DCA)3SiH. is prepared by the reaction of trichlorosilane with dicyclohexylamine. This is found to undergo transamination reactions with other secondary amines (R2NH). such as pyrrolidine, piperidine, hexamethyleneimine. morpholine. N-methylpiperazine and diethylamine to yield mixed tri(amino)silanes of the formula (DCA)(R2N)2SiH in quantitative yields. These new derivatives are found to be moisture sensitive and hydrolyze to yield their respective amines, hydrogen and silica. They are found to be stable in an inert atmosphere. They have been characterized by IR, NMR (H-1, Si-29), mass spectroscopy and CHN analysis. N-15 NMR for one of the compounds has been done.

High Yield Room Temperature Synthesis And Spectral Studies Of Tri(Amino)Silanes: (R2n)3SIH

Tri(amino)silanes were prepared by the condensation of trichlorosilane with secondary amines in 1:6 molar ratio. Reactions of trichlorosilane with pyrrolidine, piperidine, hexamethyleneimine, morpholine, N-methylpiperazine and diethylamine afford the tri(amino)silanes in nearly quantitative yields. Their physical and spectroscopic properties are discussed. All these compounds are highly sensitive to moisture and hydrolyse to silica and the respective amine with the evolution of hydrogen. The compounds have been characterised by IR, 1H NMR, [1H]29Si NMR spectroscopic methods and CHN elemental analysis.

Studies of phosphazenes .11. syntheses and structures of bis(primary amino)hexachlorocyclotetraphosphazenes and their dimethylamino derivatives

The bis(amino)hexachlorocyclotetraphosphazenes, 2-trans-6-N4P4 (NHR)2Cl6, R [dbnd] Me, Pr n Pr i , Bu n , CH2Ph, Ph, are obtained from the reaction of N4P4Cl8 with four mol. equivalents of the appropriate amine. Isomers with 2,4-structures have been isolated for R [dbnd] Bu n , CH2Ph. The 1H and 31P NMR spectra of these bis(amino) compounds and of their dimethylamino derivatives, 2-trans-6-N4P4 (NMe2)6 (NHR)2 are discussed.

Certain Aspects Related To Computation By Modified Crack Closure Integral(MCCI)

This paper presents the proper computational approach for the estimation of strain energy release rates by modified crack closure integral (MCCI). In particular, in the estimation of consistent nodal force vectors used in the MCCI expressions for quarter-point singular elements (wherein all the nodal force vectors participate in computation of strain energy release rates by MCCI). The numerical example of a centre crack tension specimen under uniform loading is presented to illustrate the approach.