几种二醇与非质子溶剂相互作用的红外光谱研究

测定了1，2-乙二醇、1，2-丙二醇、1，4-丁二醇和1，6-己二醇在CCl4中分别与十几种非质子溶剂相互作用的红外光谱，通过考察频率位移的变化，定量地研究了二醇分子内氢键与分子间氢键的协同效应．在四氯化碳介质中，乙二醇、1，2-丙二醇和1，4-丁二醇体系中存在明显的氢键协同效应。利用红外光谱数据，估算了常温下二醇分子内缔体与非质子溶剂的交叉缔合常数，其数值大于一元正链醇与相应溶剂的交叉缔合常数．     

Photorearrangements of hydrocarbon polymers with pendant double bonds

A study was made of the microstructural changes that occur in ultraviolet irradiation under vacuum of thin films of 1,2-poly(cis-1,4-hexadiene) (CHD), 1,2-poly(trans-1,4-hexadiene) (THD), 1,2-poly(trans-1,3-pentadiene) (TPD), equibinary (1,2,-1,4) polybutadiene (EB), and equibinary (3,4-1,4) polyisoprene (EI). These polymers—all containing pendant double bonds—undergo important photoinduced loss of unsaturation, presumably through cyclization of the double bonds, by analogy to the previously reported photocyclization of 1,2-polybutadiene (VB) and 3,4-polyisoprene (VI)films. For the equibinary polymers, which contain internal as well as external (or pendant) double bonds, the loss of unsaturation is considered to involve photocyclization of 1,2-1,4 and 1,2-1,2 dyads in EB and of 3,4-1,4 and 3,4-3,4 dyads in EI. Accompanying thecyclization process in CHD, THD, and TPD is a direct photochemical cis-trans isomerization of ? CH?CH? double bonds analogous to that originally noted for 1,4-polybutadiene. The photorearrangements in the above polymers with pendant double bonds were compared to the corresponding thermally induced rearrangements reported previoulsy;for VB and VI, in particular, the thermal, photo-and radiation-induced cycli-zations were found to be very similar, possibly having a common nonradical, nonionic mechanism involving excited double bonds.     

Crystal clear structural evidence for electron delocalization in 1,2-dihydro-1,2-azaborines

The first examples of "pre-aromatic" 1,2-dihydro-1,2-azaborine heterocycles have been structurally characterized, enabling the direct comparison of delocalized bonds of 1,2-dihydro-1,2-azaborines to their corresponding formal double and single bonds in nonaromatic systems. The crystallographic data provide an unprecedented look into the structural changes that occur in six-membered BN-heterocycles on their road to aromaticity, and they establish with little ambiguity that 1,2-dihydro-1,2-azaborines possess delocalized structures consistent with aromaticity.     

Thermal rearrangements of polybutadienes with different vinyl contents

A study was made of the loss of double bonds in equibinary (1,4-1,2) polybutadiene (EB) and in polybutadienes with 30% 1,2, 70% 1,4 (FI), and 10% 1,2, 90% 1,4 (DI) double-bond content, when heated in vacuum under nonpyrolytic conditions (temperature range 220–280°C). These polymers were found to undergo second-order loss of 1,2 unsaturation with similar activation energies (E_a = 34.0 ± 3 kcal/mole), by analogy to the previously reported thermally induced loss of double bonds in 1,2-polybutadiene (VB) (E_a = 33.6 ± 3 kcal/mole). Moreover, EB and FI exhibited also second-order loss of 1,4 unsaturation, with E_a ca. 36 and 40 kcal/mole, respectively, while DI showed negligible loss of 1,4 unsaturation below 260°C, in common with cis-1,4-polybutadiene (CB) (with 2% 1,2 double bonds) examined earlier. The loss of 1,2 double bonds in the various polybutadienes with different vinyl contents is accompanied by substantial methyl production, ranging from about one methyl group formed for every 4–5 vinyl units lost in VB, to one methyl for every two vinyls lost in EB, and to almost one methyl for each vinyl lost in DI or CB. Mechanisms are proposed for the thermally induced loss of 1,2 and 1,4 unsaturation in various polybutadienes and for the accompanying methyl production.     

Un nouvel hétérocycle telluré: le benzisotellurazole-1,2. 2. Structure cristalline et moléculaire du benzisoselenazole-1,2 et du benzisotellurazole-1,2

Anomalous physical properties (solubility and melting point) of 1,2-benzisotellurazole are explained by very short intermolecufar Te…N bonds (2.4 Å) found in the crystal structure. Such bonds are not present in the crystal structure of 1,2-benzisoselenazole and the physical properties are those expected.     

Surface chemistry of monochlorinated and dichlorinated benzenes on Si(100)2x1: comparison study of chlorine content and isomeric effects

Using X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD), the room temperature (RT) adsorption and thermal evolution of monochlorobenzene (MCB) and 1,3-dichlorobenzene (1,3-DCB) on Si(100)2x1 have been investigated and compared with that of 1,2-dichlorobenzene (1,2-DCB) reported previously. Like 1,2-DCB, the C 1s features observed at 284.6 (C(1)) and 286.0 eV (C(2)) for both MCB and 1,3-DCB could be attributed to the C-H and C-Cl bonds, respectively. The C(1)/C(2) intensity ratios for MCB (5.0) and 1,3-DCB (2.0) are found to follow the stoichiometric ratios of the C-H to C-Cl bonds for MCB and 1,3-DCB, respectively, indicating that both MCB and 1,3-DCB adsorb on Si(100)2x1 molecularly with negligible C-Cl dissociation at RT, in marked contrast to the partial C-Cl dissociation found for 1,2-DCB. Unlike 1,2-DCB with two discernible Cl 2s features at 270.3 and 271.2 eV, a single Cl 2s feature at 271.2 eV is observed for MCB and 1,3-DCB, in accord with the single local chemical environment for Cl. The TPD results show that MCB undergoes molecular desorption exclusively, similar to that found for benzene. Both molecular desorption and recombinative HCl desorption are found for 1,3-DCB, similar to that for 1,2-DCB. Despite the different Cl contents and relative Cl locations on the benzene ring, both MCB and 1,3-DCB exhibit RT adsorption behavior remarkably similar to that of benzene. To explain the C-Cl dissociation observed for 1,2-DCB, we propose a possible transition state involving the Cl atoms located at more physically compatible positions with the surface Si dimers in order to facilitate the conversion of 1,2-DCB (preferentially over 1,3-DCB) to dissociated products at RT. However, the thermal evolution of 1,3-DCB is closer to that of 1,2-DCB than that of MCB and benzene. The breakage of C-Cl bonds is found to occur at a relatively low temperature of 425 K, which suggests a relatively low activation barrier for the dechlorination of 1,3-DCB adspecies. Calculated energetics for 1,4-DCB on Si(100)2x1 shows that double dechlorination is not as favorable a process as those for 1,2-DCB and 1,3-DCB.     

IR spectroscopy and single crystal X-ray diffraction study of 1,2-bis(2-aminophenoxy)-ethane, 1,5-bis(2-aminophenoxy)-3-oxapentane,and 1,8-bis(2-aminophenoxy)-3,6-dioxaoctane

Vibrational spectra of 1,2-bis(2-aminophenoxy)-ethane, 1,5-bis(2-aminophenoxy)-3-oxapentane, and 1,8-bis(2-aminophenoxy)-3,6-dioxaoctane–podands, different in the length of oxyethylene fragments, are measured and their single crystal X-ray diffraction analysis is performed. It is demonstrated that the strength of intermolecular hydrogen bonds (IMHB) with the participation of NH groups increases with the elongation of the oxyethylene spacer. According to the XRD data for 1,2-bis(2-aminophenoxy)-ethane, the weakest hydrogen bonds are characteristic. From the IR spectra, important intermolecular hydrogen bonds are typical of 1,8-bis(2-aminophenoxy)-3,6-dioxaoctane having the longest oxyethylene fragment.     

CIS-Trans isomerism of a,2-bistrichlorosilylethylene

Summary The existence of cis and trans isomers of 1,2-bis-rrichlorosilylethylene was detected spectrographically. It was noted that the frequencies of the double bonds of the cis and trans isomers of 1,2-bistrichlorosilyethylene, are unusually far apart as compared with the frequencies found for the cis and trans isomers of other compounds.     

Determination of the Electron Density Distribution in the Bonds of a Fullerene Derivative by High-Resolution X-Ray Structure Analysis

Bent bonds in the strained fullerene system , restricted to the [5,6] bonds, were detected by high-resolution X-ray structure analysis of the 1,2-dihydro[60]fullerene derivative 1 . In addition the maxima of electron densities are higher in the [6,6] bonds than in the [5,6] bonds—an important finding with respect to the question of the extent of electron delocalization in fullerenes.     

Racemate resolution via diastereomeric helicates in hydrogen-bonded co-crystals: the case of BINOL–diamine complexes

The structures of a series of co-crystals formed by enantiomers of BINOL (2,2′-dihydroxy-1,1′-binaphthalene) with (R,R)-1,2-diaminocyclohexane (DACH) and (R,R)-1,2-diamino-1,2-diphenylethane have been determined by X-ray diffraction to investigate the factors responsible for diastereoselective co-crystallization, the process responsible for the highly effective resolution of rac-BINOL by DACH. The absolute configurations of the molecules and directional preferences of the hydrogen bonds in the supramolecular aggregates have been analyzed. The supramolecular aggregation of hydrogen-bonded BINOL and diamines shows considerable distortions from the helical shape, which indicates that cohesion forces other than hydrogen bonds play a significant role in the diastereoselective resolution.     

Synthesis of 2,3-di- and 2,3,4-trisubstituted furans from 1,2-dioxines generated by an enyne-RCM/Diels-Alder reaction sequence

An efficient method for the synthesis of 2,3- and 2,3,4-substituted furans starting from acyclic enynes was developed using an enyne-RCM/Diels-Alder reaction sequence. The reaction conditions for the transformation of 1,2-dioxines having an adjacent 1,2-oxazine ring into furans and the cleavage of N-O bonds are discussed.     

Epoxidation of syndiotactic 1,2-polybutadiene with peracids

The epoxidation of syndiotactic 1,2-polybutadiene (84 and 16% 1,2 and 1,4 units, respectively) with carboxylic peracids prepared in situ and m-chloroperbenzoic acid was studied. In the course of epoxidation in the presence of carboxylic peracids, oxirane groups are formed only through epoxidation of double bonds in the macromolecular backbone, whereas m-chloroperbenzoic acid is responsible for the chemical modification of 1,2 and 1,4 units of polybutadiene. The basic kinetic parameters of 1,2-polybutadiene epoxidation with peracids of various chemical structures were determined.     

甲亚胺1,2—脱氢过程中化学键变化的量子拓扑研究

在IRC解析的基础上,用电子密度的量子拓扑分析方法研究了甲亚胺1,2-脱氢过程中化学键的变化.反应途径中各点化学键的拓扑性质可以清楚地反映出化学键断裂及生成过程,计算结果进一步证明该反应为协同非同步反应.本工作为研究化学反应过程提供了一种新的方法。     

Synthesis of kinetically stabilized 1,2-dihydrodisilenes

Kinetically stabilized 1,2-dihydrodisilenes were successfully synthesized and isolated by the introduction of sterically protecting bulky aryl groups. These 1,2-dihydrodisilenes exhibit distinct Si═Si double-bond character in both solution and the solid state. The Si-H bonds in these 1,2-dihydrodisilenes exhibit higher s character than those of typical σ(4),λ(4)-hydrosilanes. Moderate heating of these 1,2-dihydrodisilenes in solution resulted in their isomerization to the corresponding trihydrodisilanes, with an intramolecular hydrogen migration as the rate-determining step.     

A stable enol in small ring systems: clear differentiation between penta- and tri-valency of phosphorus atoms

The first stable enols in 1,2-dihydrophosphetes and were synthesized and structurally characterized with intermolecular hydrogen bonds to phosphoryl groups in 10-membered dimeric structures; in contrast, trivalent analogue exists in keto-form, where such stabilization by hydrogen bonds is not feasible.     

Vibrational spectra of cyclopropenes. II. IR spectra of 1,2-disubstituted cyclopropenes

The IR spectra were measured and the vibrational problem was solved for the 1,2-dimethyl-3-phenylcyclopropene (I) and 1,2-diphenylcyclopropene (II) molecules. The forms of the normal vibrations were determined, and the vibrations associated with vibrations of the exo- and endocyclic bonds of the ring were distinguished. It was shown that substitution at the double bond of cyclopropene leads to a change in the form of the symmetrical vibration of the ring in comparison with the vibration of unsubstituted cyclopropene. It was shown that a significant hypsochromic shift of the band of the symmetrical ring vibration in 1,2-disubstituted cyclopropenes in comparison with cyclopropenes that do not contain substituents at the C^1,2 atoms is due chiefly to the kinematic effect of the substituent. It was found that the introduction of substituents at the double bond of the ring leads to a decrease in the force constant of the double bonds.St. Petersberg University. Translated from Zhurnal Strukturnoi Khimii, Vol. 34, No. 1, pp. 125–132, January–February, 1993.     

Rearrangement pathways of 2-hydroxy-2-methylpropylidene: an experimental and computational study

Photolysis of exo-2-(1a,9b-dihydro-1H-cyclopropa[l]phenanthren-1-yl)propan-2-ol in benzene-d(6) afforded phenanthrene and the beta-hydroxycarbene intermediate 2-hydroxy-2-methylpropylidene. The carbene showed an overwhelming preference for 1,2-methyl migration as evident from the formation of 2-butanone as the major product via the enol 2-hydroxy-2-butene. Also produced, albeit in smaller amounts, were 1-methylcyclopropanol and 2,2-dimethyloxirane from intramolecular insertion into the C-H and O-H bonds, respectively. These results stand in sharp contrast to the intramolecular reactions of simple alkylcarbenes which usually prefer insertion into C-H bonds over 1,2-alkyl migrations. Calculations at the B3LYP/6-311+G//B3LYP/6-31G level of theory give a lower activation barrier for 1,2-methyl migration leading to the eventual formation of 2-butanone than for the other two pathways. The lower activation energy for methyl migration, relative to C-H and O-H insertions, strongly supports the observed experimental product distribution of the carbene. The parent carbene exists in three distinct conformations, each with stabilizing interactions between the adjacent bonds and the empty p orbital and the filled sp(2) orbital of the carbene center. The most stable conformer is perfectly poised for a 1,2-methyl migration as the C-CH(3) group is involved in a hyperconjugative interaction with the empty p orbital and the O-H bond is simultaneously interacting with the sp(2) lone pair of the carbene.     

Improved method for the diimide reduction of multiple bonds on solid-supported substrates

A mild and improved method for reducing multiple bonds on various resins with diimide is described. The simple procedure readily generates diimide from 2-nitrobenzenesulfonohydrazide and triethylamine at room temperature. A number of representative multiple bonds in various steric and electronic environments were examined, including polar double bonds such as carbonyl and azo, for ease and selectivity of reduction. A general trend of reactivity was identified which revealed, inter alia, that terminal olefins, 1,2-disubstituted olefins, electron-poor olefins, and terminal alkynes were the most easily reduced.     

Quantumchemical Investigation of Unsaturated Sixmembered Heterocycles: I. Steric and Electronic Structures of 1,2-dihydro-1,2-azaphosphorin

By quantumchemical calculations of 1,2-dihydro-1,2-azaphosphorin by semiempirical and abinitio calculations we discovered that in gas phase it has twist form with planar nitrogen and pyramidal phosphorus atoms, the latter with a pseudoaxial substituent. The N-H and P-H bonds occupy anticlinal positions.     

Synthesis and characterization of amidate bridged dimeric and oligomeric platinum complexes having short platinum-platinum interactions

A number of pivalamidate bridged dinuclear [PtII2(RNH2)4(NHCOtBu)2]2+, [PtIII2LL (RNH2)4(NHCOtBu)2]n+ (2RNH2 = 2NH3, 1,2-ethylenediamine, 1,2-diaminocyclohexane; L, L' = NO3-, H2O, or ketonate), trinuclear [{PtII(dap)(NHCOtBu)2}2PdIII]3+ (dap = 1,2-diaminopropane), tetranuclear [{PtII2(NH3)2(DACH)(NHCOtBu)2}2]4+ (DACH = 1,2-diaminocyclohexane), pentanuclear [{Pt2(C5H7O)(NH3)2Cl2(NHCOtBu)2}2PtCl4], and hexanuclear [Pt2(NH3)2(en)(NHCOtBu)2Pt(NO2)4]2 platinum complexes containing Pt(II)-Pt(II), Pt(II)-Pt(III), Pt(II)-Pd(III), and Pt(III)-Pt(III) interactions have been prepared and structurally characterized. The Pt-Pt interactions are characteristic of covalent, dative, or orbital symmetric Pt-Pt bonds. The dimeric Pt(III) complexes are able to activate C-H bonds of ketones to afford ketonate platinum(III) complexes. The Pt-Pt bonds are either doubly amidate-bridged or ligand unsupported. Their distances are 2.99-3.22 A for Pt(II)-Pt(II), 2.59-2.72 A for Pt(III)-Pt(III), 2.98 A for Pt(II)-Pt(III), and 2.66 A for Pt(II)-Pd(III) bonds depending on the oxidation states of the two metals and the ancillary ligands.