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1.
The barrier to the internal rotation of the dimethylamino group in thioamides of structure R? CS? N(CH3)2, R being (CH3)2,N? CS? , CH3O2C? or N?C? , is studied by proton magnetic resonance, using the lineshape analysis method of Nakagawa. In the solvents o-dichlorobenzene, naphthalene and nitrobenzene all ΔG≠ values are in the range of 23 to 24 kcal/mol. In these solvents the Ea and ΔS≠ values of each product are linearly related to the dielectric constants.  相似文献   

2.
Crystal structures of a series of manganese(I) complexes containing tripodal ligands were determined. For [η3-{CH3C(CH2PPh2)2(CH2SPh)-P,P′,S}Mn(CO)3]PF6 ( 1 ): a = 10.856(3) Å, b = 19.698(3) Å, c = 17.596(5) Å, β = 96.17(2)°, monoclinic, Z = 4, P21/c, R(Fo) = 0.068, Rw(Fo) = 0.055 for 3617 reflections with Io > 2σ(Io). For [η3-{CH3C(CH2PPh2)(CH2SPh)2-P,P′,S}Mn(CO)3]PF6 ( 2 ): a = 9.890(2) Å, b = 20.403(4) Å, c = 10.269(3) Å, β = 117.44(2)°, monoclinic, Z = 2, P2l, R(Fo) = 0.050, Rw(Fo) = 0.037 for 1760 reflections with Io > 2σ(Io). For [η3-{CH3C(CH2PPh2)2(CH2S)-P,P′,S}Mn(CO)3] ( 4 ): a = 8.191(7) Å, b = 10.495(3) Å, c = 19.858(6) Å, α = 99.61(2)°, β = 96.17(2)°, γ = 92.70(4)°, triclinic, Z = 2, P-I, R(Fo) = 0.048, Rw(Fo) = 0.039 for 2973 reflections with Io > 2σ(Io). There is no significant difference in the bond lengths of Mn-S bonds among three species in their crystal structures [2.325(2) Å in 1; 2.358(4) in 2; 2.380(2) in 4], but the better donating ability of thiolate in complex 4 appears on the lower frequencies of its carbonyl stretching absorptions.  相似文献   

3.
The electron-impact (EI) mass spectral fragmentation of ten bis-O- (1-methylethylidene)fructopyranose derivatives and three related sugar sulfamates were investigated. In particular, 2,3:4,5-bis-O - (1-methylethylidene)-β-D-fructopyranose sulfamate (topiramate), a potent anticonvulsant, was examined in greater detail. The fragmentation of the 2,3:4,5-bis-O-(1-methylethylidene) fructopyranose derivatives in general was not very dependent on the nature of substitution; the mechanisms of the common and unique fragmentation patterns are presented. These compounds showed characteristic peaks at m/z [M – 15]+, [M – 15 – 58]+, [M – 15 – 58 – 60]+, [M ? CH2X]+ and [M ? CH2X – 58]+ where X = OSO2NR2 (R ? H, CH3, and/or Ph), OC (O)NHR, NH2, CI and OH. The fragmentation of isomeric bis-O-(1-methylethylidene) derivatives of aldopyranose, ketopyranose and ketofuranose sulfamates was also investigated. The results indicate that isomeric sugar sulfamates can be easily distinguished in the EI mode. Key fragmentation pathways are discussed for these compounds.  相似文献   

4.
The new α,ω-[boryl(organyl)]phosphane o-Ph2PC6H4CH2B (NMe2)2 ( 10 ) was obtained in good yields from the reaction of CIB(NMe2)2 with o-Ph2PC6H4CH2Li(tmeda). Five derivatives of 10 were obtained by substituting the boron-bound amino groups by reactions with MeOH, BCl3, HCl, and LiAlH4, respectively, in particular, o-Ph2(HCl)PC6H4CH2BCl2 (HNMe2) ( 10 e ) which shows a unique P? H? Cl? H? N unit. Compound 10 and its derivatives were characterized by multinuclear NMR methods, mass spectra, and elemental analyses. In addition, the structure of 10 e · 1.5 C6H6 was determined by single crystal X-ray diffraction.  相似文献   

5.
From deuterium labelling experiments it was concluded that metastable molecular ions of ethyl methyl sulfide lose a methyl radical with the formation of both [CH3S?CH2]+ amd [CH3CH?SH]+˙ The fragmentation reactions of metastable ions generated with these structure are losses of C2H2, H2S and CH4. These reactoins and the preceding isomerizations have also been studied by means of deuterium labelling. From the results it is concluded that the three fragmentation reactions most probably occur from ions with a C? C? S skeleton. Appearance energy measurements for ions generated with the two structures above and all give rise to the same ΔHf value for these three isomeric forms. Ab initio molecular orbitals calculations confirm that these three ions fortuitously have very similar heats of formation. A potential energy diagram rationalizing the isomerizations and the principal fragmentation reaction is presented.  相似文献   

6.
The mass spectra of two series of aliphatic polynitro compounds are reported and discussed. The fragmentation patterns of aliphatic nitro and polynitro compounds are similar in that no appreciable molecular ion current is observed; however, there are several other features in the fragmentation of aliphatic polynitro compounds which differ from that of nitroalkane spectra. Both series of compounds studied-C(NO2)x(CH3)4?x, where x = 4 to 0 and C2(NO2)x(CH3)6?x, where x = 6,4,2-show a decrease in the number and intensity of alkylions with an increase in the NO+ and NO2+ ion current as x increases. The main ions resulting from the more nitrated compounds are [NO]+, [NO2]+, [CO2]+. and [CH3CO]+, whose noncharged counterparts are the principal species produced in the detonation of these compounds. This similarity of the products of the two processes suggests the use of mass spectroscopy for the investigation of the initial explosive processes. The principal fragmentation pathways of the polynitroalkanes have been elucidated by exact mass measurements and the observation of metastable ion transitions.  相似文献   

7.
The fragmentation reaction [C3(H,D)6]+· → [C3(H,D)5]+ + (H, D) has been examined in the metastable decomposition region for two pairs of labelled propenes: CH3CD?CH2,CD3CH?CD2 and CD3CH?CH2, CH3CD?CD2. The results indicate that complete hydrogen scrambling occurs in the propene molecular ion prior to fragmentation. The isotope effect kH/kD is in the range 2·1 to 3·3.  相似文献   

8.
The electron-impact induced fragmentation of 6-chloro-6H-dibenz[c,e] [1,2]oxaphosphorine-6-sulphide and its 6-ethoxy and 6-hydroxy derivatives has been studied and it has been found that formation of the dibenz[c,e] [1,2]oxaphosphorin system and elimination of HCP are common features. β-Hydrogen rearrangement, in the case of the ethoxy derivative, is comparable to ethers with a P? O? CH2? CH3 linkage.  相似文献   

9.
Using four basis bets, (6‐311G(d,p), 6‐31+G(d,p), 6‐31++G(2d,2p), and 6‐311++G(3df,3pd), the optimized structures with all real frequencies were obtained at the MP2 level for the dimers CH2O? HF, CH2O? H2O, CH2O? NH3, and CH2O? CH4. The structures of CH2O? HF, CH2O? H2O, and CH2O? NH3 are cycle‐shaped, which result from the larger bend of σ‐type hydrogen bonds. The bend of σ‐type H‐bond O…H? Y (Y?F, O, N) is illustrated and interpreted by an attractive interaction of a chemically intuitive π‐type hydrogen bond. The π‐type hydrogen bond is the interaction between one of the H atoms of CH2O and lone pair(s) on the F atom in HF, the O atom in H2O, or the N atom in NH3. In contrast with the above three dimers, for CH2O? CH4, because there is not a π‐type hydrogen bond to bend its linear hydrogen bond, the structure of CH2O? CH4 is noncyclic shaped. The interaction energy of hydrogen bonds and the π‐type H‐bond are calculated and discussed at the CCSD (T)/6‐311++G(3df,3pd) level. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005  相似文献   

10.
(RCp)(R′Ind)ZrCl2 complexes 1 – 6 (Cp = cyclopentadienyl; Ind = indenyl; 1 , R = PhCH2 and R′ = H; 2 , R = PhCH2 and R′ = PhCH2; 3 , R = PhCH2CH2 and R′ = H; 4 , R = PhCH2CH2 and R′ = PhCH2; 5 , R = o‐Me? PhCH2CH2 and R′ = H; 6 , R = o‐Me? PhCH2 and R′ = H) were synthesized and characterized with 1H NMR, elemental analysis, mass spectrometry, and infrared spectroscopy. Their catalytic behaviors were compared with those of (Et3SiCp)(PhCH2CH2Cp)ZrCl2, (PhCH2Cp)2ZrCl2, (PhCH2‐ CH2Cp)2ZrCl2, (o‐Me? PhCH2CH2Cp)2ZrCl2, and (Ind)2ZrCl2 in ethylene polymerization in the presence of methylaluminoxane. Complex 5 showed high activity up to 2.43 × 106 g of polyethylene (PE)/mol of Zr h, and complex 4 produced PE with bimodal molecular weight distributions. The methyl group at the 2‐position of phenyl in complex 5 increased the activity greatly. The relationships between the polymerization results and the structures were analyzed with NMR spectral data. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1261–1269, 2005  相似文献   

11.
Optically active cyclopropanes (e.g. 1 ) can be prepared by the use of tartaric acid derivatives as chiral auxiliaries in the palladium-catalyzed cross-coupling of optically active cyclopropylboronic acids with electrophiles. The absolute configuration of the chiral carbon atom is retained, and the reaction proceeds with good yields and enantiomeric excesses. R=H, p-Ph, o-CO2CH3, p-CO2CH3, p-NO2, o-OCH3, m-OCH3.  相似文献   

12.
Abstract —On photoexcitation, hydroxyacetone undergoes a Norrish-type-1 fragmentation to yield CH3CO and CH2OH. CH2OH is identified by its EPR spectrum. The existence of CH3CO is inferred from the presence of diacetyl and acetaldehyde in irradiated solutions. Above pH 5, in addition to CH2OH, the cis and trans forms of the hydroxyacetone enediol radical anion, CH3C(O-)=C(O***)H, are detected. 1.3-Dihydroxyacetone is photodecomposed to HOCH2C?O and C?H2OH. The former radical decarbonylates to yield CH2OH and CO. At 254 nm the overall quantum yield of CO production is 0.75. Above pH 5, in addition to CH2OH, the cis and trans forms of the 1.3-dihydroxyacetone enediol radical anion, HOCH2C(O-)C(O***)H, are observed. Electronically excited hydroxyacetone and 1.3-dihydroxyacetone react exclusively by C-C fragmentation, and no H-abstraction from H-donors is observed. In contrast, electronically excited 1.3-dicarboxyacetone shows H-abstraction from H-donors in competition with C-C fragmentation. In the absence of H-donors, fragmentation resulting in CH2CO2- and -O2CCH2C?O occurs followed by decarbonylation of -O2H2C?O. At 254 nm the quantum yield of CO production is 0.02. In the presence of H-donors, H-abstraction, yielding HO2CCH2C(OH)CH2CO2, predominates.  相似文献   

13.
Using four basis sets, 6‐311G(d,p), 6‐31+G(d,p), 6‐311++G(2d,2p), and 6‐311++G(3df,3pd), the optimized structures with all real frequencies were obtained at the MP2 level for dimers CH2O? HF, CH2O? H2O, CH2O? NH3, and CH2O? CH4. The structures of CH2O? HF, CH2O? H2O, and CH2O? NH3 are cycle‐shaped, which result from the larger bend of σ‐type hydrogen bonds. The bend of σ‐type H‐bond O…H? Y (Y?F, O, N) is illustrated and interpreted by an attractive interaction of a chemically intuitive π‐type hydrogen bond. The π‐type hydrogen bond is the interaction between one of the acidic H atoms of CH2O and lone pair(s) on the F atom in HF, the O atom in H2O, or the N atom in NH3. By contrast with above the three dimers, for CH2O? CH4, because there is not a π‐type hydrogen‐bond to bend its linear hydrogen bond, the structure of CH2O? CH4 is a noncyclic shaped. The interaction energy of hydrogen bonds and the π‐type H‐bond are calculated and discussed at the CCSD(T)/6‐311++G(3df,3pd) level. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005  相似文献   

14.
New Horner–Wadsworth–Emmons reagents, (o-t-BuPhO)2P(O)CH2CONMe(OMe) and (o-t-BuPhO)2P(O)CH2CON(CH2CH2) 2O were prepared via the Arbuzov reaction in good yields. The HWE reaction of these reagents with a variety of aldehydes gave cis-α,β-unsaturated amides with high selectivity in almost quantitative yields.  相似文献   

15.
Cyclic polysulfides isolated from higher plants, model compounds and their electron impact induced fragment ions have been investigated by various mass spectrometric methods. These species represent three sets of sulfur compounds: C3H6Sx (x=1?6), C2H4Sx (x=1?5) and CH2Sx (x=1?4). Three general fragmentation mechanisms are discussed using metastable transitions: (1) the unimolecular loss of structural parts (CH2S, CH2 and Sx); (2) fragmentations which involve ring opening reactions, hydrogen migrations and recyclizations of the product ions ([M? CH3]+, [M? CH3S]+, [M? SH]+ and [M? CS2]); and (3) complete rearrangements preceding the fragmentations ([M? S2H]+ and [M? C2H4]). The cyclic structures of [M] and of specific fragment ions have been investigated by comparing the collisional activation spectra of model ions. On the basis of these results the cyclic ions decompose via linear intermediates and then recyclizations of the product ions occur. The stabilities of the fragment ions have been determined by electron efficiency vs electron energy curves.  相似文献   

16.
In this study phenylselenocyanate and some of its derivatives (o‐Cl, p‐Cl, p‐Br, o‐NO2, p‐NO2, o‐CH3, p‐CH3, o‐COOH, p‐COOH, p‐OCH3 substituted) were synthesized ( 3a–3j ). The synthesized compounds were converted to 5‐aryl‐1H‐tetrazole ( 4a–4j ), by Et3N ċ HCl‐NaN3 in toluene, which are a new series of phenylselanyl‐1H‐tetrazoles. The structure of all the presently synthesized compounds were confirmed using spectroscopic methods (FTIR, 1H NMR, MS). © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:255–258, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20293  相似文献   

17.
The 70 eV mass spectrum of phenyl ω-dimethoxyethyl telluride [C6H5? Te? CH2CH(OR)2, R?CH3]contains an intense peak at m/z 238 which corresponds to a rearrangement ion [C6H5? Te? OR]+. The formation of this species is further illustrated by the presence of a peak at m/z 241 in the spectrum of the hexadeuterated analog (R?CD3) and a peak at m/z 252 in the spectrum of the ethyl analog (R?CH2CH3). These combined results illustrate the presence of only one of the alkoxyl groups in the rearrangement ion. Several other abundant ions that contain oxygen but not tellurium are present in the spectra of these compounds. High resolution analyses have aided in the determination of the origin and composition of several of the characteristic ions formed upon electron impact fragmentation of phenyl ω-dimethoxyethyl telluride.  相似文献   

18.
A detailed energy-resolved study of the fragmentation of CH2?CHCH(OH)CD2CD3 (1-d5) has been carried out using metastable ion studies and charge exchange techniques, combined with collision-induced dissociation studies to establish the structures of fragment ions. At low internal energies (metastable ions) the molecular ion of 1-d5 rearranges to the 3-pentanone structure and fragments by loss of C2H5 or C2D5 leading to the acyl structure, [CH3CH2C?O]+ or [CD3CD2C?O]+, for the fragment ion. However, with increasing internal energy of the molecular ion this rearrangement process decreases rapidly in importance and loss of C2D5 by direct cleavage, leading to [CH2?CHCH?OH]+, becomes the dominant fragmentation reaction. As a result the [C3H5O]+ ion seen in the electron impact mass spectrum of 1-penten-3-ol has predominantly the protonated acrolein structure.  相似文献   

19.
The electron impact (EI) ionization-induced fragmentation pathways of the new 1,9-bis(dimethylamino) phenalenium cation [1]+ were investigated. The peri-dimethylamino substituents of [1]+ are incorporated in a trimethine cyanine substructure and show strong steric interactions. A mechanism is proposed for the unusual elimination of CH3N?CH2, HN(CH3)2 and (CH3)3N from [1]+ and for the accompanying cyclizations to heterocyclic ions: prior to fragmentation, the intact cation [1]+ rearranges, by reciprocal CH3 and H transfers, to new isomeric cations which decompose subsequently in a characteristic way. A wealth of consistent information on dissociation pathways and fragment structures is provided by collision-induced dissociation tandem mass spectra, collision-induced dissociation mass-analysed ion kinetic energy spectra and exact mass measurements of the salt cation and of its primary fragment ions. The liquid secondary ion mass spectrum of [1]+ is very similar to its EI mass spectrum.  相似文献   

20.
The behaviour under electron impact (70 eV) which includes some rearrangement processes of some tetraorganodiphosphanedisulfides R2P(S)-P(S)R2 (R ? CH3, C2H5, n-C3H7, n-C4H9, C3H5, C6H5) and CH3RP(S)–P(S)CH3R (R ? C2H5, n-C3H7, n-C4H9, C6H5, C6H5, C6H5,CH2) is reported and discussed. Fragmentation patterns which are consistent with direct analysis of daughter ions and defocusing metastable spectra are given. The atomic composition of many of the fragment ions was determined by precise mass measurements. In contrast to compounds R3P(S) loss of sulphur is not a common process here. The first step in the fragmentation of these compounds is cleavage of one P–C bond and loss of a substituent R?. The second step is elimination of RPS leading to [R2PS]+ from which the base peaks in nearly all the spectra arise. The phenyl substituted compounds give spectra with very abundant [(C6H5)3P]+. and [(C6H5)2CH3P]+. ions respectively, resulting from [M]+. by migration of C6H5. Rearrangement of [M]+. to a 4-membered P-S ring system prior to fragmentation is suggested.  相似文献   

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