Combinations of alkyl radicals with alkyl and substituted allyl radicals

In contrast with expectations based upon simple collision theory, reactions of alkyl radicals with substituted allyl radicals yield cross-combination ratios of =2. Reactions of CH ₃ ^\ with some C₅ radicals give >2, in accordance with theory.

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, =2. CH₃ ^\ C₅ >2, .

     

MINDO-SCF-MO-berechnung der cis-trans-isomerisierung von N-methyl- und N-phenylazomethin

MINDO/2-SCF-MO calculations for the ground state properties of N-methyl- and N-phenyl-azomethin have been carried out. The calculated rotation barrier for the methyl group in N-methyl-azomethin was 0·8 kcal/mol, the eclipsed conformation being most stable. The calculated rotation barrier about the CN bond in the protonated methylazomethin was 27·9 kcal/mol. MINDO/1-SCF-MO treatment for the N-inversion barrier of the unprotonated species yielded 13·00 kcal/mol. Similar MINDO/2 calculations for N-phenylazomethin yielded 4·0 kcal/mol for the rotation barrier of the phenyl ring around the CN= bond, the perpendicular conformation of the ring to the CNC plane being most stable. For the corresponding N protonated derivative the value 27·3 kcal/mol was calculated for the rotation barrier around the CN bond. MINDO/1 treatment yielded an inversion barrier of 14·0 kcal/mol for N-phenylazomethin.     

Soluble alkyl substituted polygermanes: Thermochromic behavior

We have prepared a number of high molecular weight, soluble, symmetrical dialkyl substituted germanium homopolymers and germanium-silicon copolymers. In solution, the absorption of the homopolymers was ～ 20 nm red shifted from the crossponding silicon derivatives. This was somewhat unexpected based on theoretical predictions and has been rationalized on the basis of conformational arguments. In the solid state, samples of poly(di-n-hexylgermane) and poly(di-n-octylgermane) are strongly thermochromic. The effect is attributed to the conformational locking of the backbone which is caused by the crystallization of the side groups. In this regard, the germanium derivatives behave similarly to the corresponding silicon polymers, and the convergence of the long wavelength absorptions for both types of polymers is consistent with theoretical predictions. The germanium-silicon copolymers are also strongly thermochromic, but the long wavelength absorption is somewhat blue shifted (8 nm) from the respective homopolymers. As expected, the new germanium homo and copolymers are quite sensitive to light and readily undergo chain scission to produce lower molecular weight materials.     

Properties of some alkyl substituted phthalocyanines and related macrocycles

This report provides an account of research undertaken at the University of East Anglia, United Kingdom, into phthalocyanine derivatives substituted at six or more of the nonperipheral sites by alkyl groups. When first prepared they were only the second series of substituted phthalocyanines known to exhibit columnar liquid crystal behaviour. The compounds also form structured films by the spin-coating technique, a formulation with potential for FET devices. The zinc metallated derivatives are photosensitisers of singlet oxygen and show good potential for applications in photodynamic therapy. A mixed cyclotetramerisation of a 3,6-dialkylphthalonitrile with a second aromatic dinitrile forms so-called 3 : 1 phthalocyanines in which three of the benzenoid rings are substituted with two alkyl groups and the fourth is substituted differently. Appropriate substituents provide amphiphilic compounds that form well-ordered films by the Langmuir-Blodgett method and self-assembly techniques. Characterisation of the films using a variety of methods is discussed and applications described. Examples of 3 : 1 phthalocyanine-like macrocycles in which one of the benzenoid rings is replaced by a heterocycle extend the range of properties exhibited. These include broadband absorption in the near infrared and, in particular cases, edge-to-face dimerisation through coordination of a pyridine nitrogen to a zinc centre in a second macrocycle. The potential for using suitably functionalised 3 : 1 phthalocyanines as building blocks for more complex structures such as liquid crystalline main-chain polymeric phthalocyanines and phthalocyanino-dehydroannulenes is described.     

Adsorption of alkyl polyglucosides on the solid/water interface: equilibrium effects of alkyl chain length and head group polymerization

The equilibrium adsorption behavior of two n-alkyl-beta-D-glucosides (octyl (C8G1) and decyl (C10G1)) and four n-alkyl-beta-D-maltosides (octyl (C8G2), decyl (C10G2), dodecyl (C12G2), and tetradecyl (C14G2)) from aqueous solution on a titania surface, as measured by ellipsometry, has been investigated. The main focus has been on the effect of changes in the alkyl chain length and headgroup polymerization, but a comparison with their adsorption on the silica/water and air/water interfaces is also presented. Some comparison with the corresponding adsorption of ethylene oxide surfactants, in particular C10E6 and C12E6, is given as well. For all alkyl polyglucosides, the maximum adsorbed amount on titania is reached slightly below the critical micelle concentration (cmc), where it levels off to a plateau and the amount adsorbed corresponds roughly to a bilayer. However, there is no evidence that this is the actual conformation of the surfactant assemblies on the surface, but the surfactants could also be arranged in a micellar network. On hydrophilic silica, the adsorbed amount is a magnitude lower than on titania, corresponding roughly to a layer of surfactants lying flat on the surface. A change in the alkyl chain length does not result in any change in the plateau molar adsorbed amount at equilibrium; however, the isotherm slope for the alkyl maltosides increases with increasing chain length. Headgroup polymerization on the other hand affects the adsorbed amount. The alkyl glucosides start adsorbing at lower bulk concentrations than the maltosides and equilibrate at higher adsorbed amounts above the cmc. When compared with the ethylene oxide (EO) surfactants, it is confirmed that the EO surfactants hardly adsorb on titania, since the measured changes in the ellipsometric angles are within the noise level. They do, however, adsorb strongly on silica.     

Electrochemically induced chain transformation of salicylaldehydes and alkyl cyanoacetates into substituted 4H-chromenes

Electrolysis of salicylaldehydes and alkyl cyanoacetates in ethanol in an undivided cell in the presence of sodium bromide results in the formation of substituted alkyl 2-amino-4-(1-cyano-2-alkoxy-2-oxoethyl)-4H-chromene-3-carboxylates in 85-95% yields.     

The electronic spectra of the alkyl,fluorine and chlorine substituted derivatives of silane

The main characteristics of the ultraviolet absorption spectra of simple alkyl, fluorine and chlorine derivatives of silane are described. The interpretation of these spectra is discussed in relation to the respective photoelectron spectra, the Rydberg-valence-shell distinction and involvement of 3d atomic orbitals.Dedicated to Professor Dr. Hermann Hartmann on the occasion of his 65th birthday.     

Synthesis of fluorinated cyclic s-trans vinylogous acid and amide ester derivatives

A two-step procedure for the preparation of ethyl 4-amino-2-oxo-6-(trifluoromethyl)cyclohex-3-ene-1-carboxylate (enaminone) and methyl 4-hydroxy-2-oxo-6-(trifluoromethyl)cyclohex-3-ene-1-carboxylate (vinylogous acid) has been accomplished, using reactive Michael acceptors under basic condition. In addition, acyclic trifluoromethylated ester derivatives were isolated as competing by-products. The above compounds represent novel synthetically useful trifluoromethyl building blocks.     

Alkyl and dialkylammonium tetrafluoroborate catalyzed cis-trans isomerization of 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane

Alkyl and dialkylammonium tetrafluoroborate promoted cis-trans isomerization of 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane (1) in DMSO-d₆ were studied. The isomerization equilibrium constant K are within the range of 3.74-3.30 from 22 to 47 °C. Thermodynamic parameters of ΔH° and ΔS° for the isomerization were −0.95 kcal/mol and −0.59 cal/mol-K respectively. The isomerization rate is first order in [cis-1] and second order in [R_nNH_4−nBF₄]. Both components of R_nNH_4−n⁺ and BF₄⁻ are essential for the catalytic cis-trans isomerization. The catalytic strength follows the decreasing order of ⁺H₃N(CH₂)₆NH₃⁺>n-C₈H₁₇NH₃⁺>n-C₁₆H₃₃NH₃⁺>Me₃CNH₃⁺>PhCH₂NH₃⁺>Et₂NH₂⁺?Ph₂CHNH₃⁺, Et₃NH⁺. Inversion region was observed in the plot of ln(k_f/T) versus (1/T) with the ceiling located at around 38 °C. The positive activation enthalpy of 9 kcal/mol was estimated at 22-32 °C. The activation enthalpy turns to be slightly negative at T>38 °C.     

On the chemical ionization reactions of alkyl substituted cyclopropanes

As predicted by semi-empirical molecular orbital calculations, the methane chemical ionization mass spectra of alkylcyclopropanes exhibit both proton addition and hydride abstraction processes; both the calculations and the observed substituent effects suggest the common intermediacy of gas phase cyclopropylcarbinyl cations. In agreement with this hypothesis are the results of an isotopic labeling experiment which identifies the reactive site as the cyclopropylcarbinyl carbon.     

Conversion of a trans-syn-trans to a cis-syn-trans perhydrobenz[e]indenone triggered by intramolecular 1,5-hydrogen transfer

The conversion of a trans-syn-trans perhydroiodomethyltrimethylbenz[e]indenone to the corresponding cis-syn-trans perhydrobenz[e]indenone occurred during the reduction of the iodomethyl to a methyl group under radical conditions.     

A comparative study of some oxygen and sulphur substituted alkyl radicals

Several sulphur containing alkyl radicals have been generated and their ESR spectra and hyperfine coupling constants compared with those of the oxygen analogues. Deviations from planarity are smaller when a tervalent carbon atom is bonded to sulphur than when bonded to oxygen. Moreover greater delocalization of the unpaired electron is apparent in the sulphur radicals and this leads to higher barriers to internal rotation in radicals of the form H₂SR compared with H₂OR.     

Kinetics of the reactions of substituted benzoquinones with alkyl radicals

Conclusions Study has been made of the kinetics of the reactions of sec-decyl radicals with 2,6-di-tert-butyl-, and 2,6-diphenyl-p-benzoquinone, and 2,4- and 2,5-di-tert-butyl-o-benzoquinones at 50°C. Rate constants and inhibition coefficients have been determined for these reactions.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2487–2491, November, 1978.     

1'-长链烷基取代吲哚啉螺苯并噻喃的合成及光谱性质

本文报道七个新的1'-长链烷基取代吲哚啉螺苯并噻喃衍生物的合成以及它们在溶液和高分子介质中的光致变色反应和吸收光谱性质。     

十八烷基取代吲哚啉螺吡喃衍生物的合成及光谱性质

本文合成了十种新的十八烷基取代的吲哚螺吡喃衍生物,拟进一步研究这类化合物在LB膜中的光致变色性质.     

Ground state and excited state dipole moments of alkyl substituted para-nitroaniline derivatives

The ground state and excited state dipole moment of a series of alkyl substituted para-nitroaniline derivatives is reported. Ground state dipole moment was determined by the Debye-Guggenheim method and the excited state dipole moment was estimated using the solvatochromic method. For all molecules under investigation, the excited state dipole moment was found to be higher than the ground state dipole moment. The molecules exhibited positive solvatochromism.     

The synthesis of alkyl substituted 2-pyrazolines by the reaction of acids with hydrazine derivatives

A convenient synthesis of alkyl substituted 2-pyrazolines (III) has been developed from the reaction of acids with hydrazones (I) and azines (IV). An alkylidenebis-1-methyl-2-alkylidene-hydrazine (V) was isolated as an intermediate, in the preparation of 5-isopropyl-1,4,4- trimethyl-2-pyrazoline (IIId), and protonated vinylhydrazones (II) are proposed as common intermediates in the formation of III, IV and V. The 4,5-dialkyl-2-pyrazolines (IIIk-m) that were prepared were shown to be free of isomers by nmr. The thermal isomerization of IIIk-m to 3,4-dialkyl-2-pyrazolines (IIIn-o) was found to be incomplete at the temperatures studied. The reaction of IIIn-o with acetone afforded 3,4-dialkyl-1-[2-(2-methyl-4-oxopentyl)]-2-pyrazolines (IIIp-q). The nmr and mass spectral data of III are discussed.     

A molecular orbital study of the cis-trans energy difference in glyoxal

The barrier to internal rotation around the C-C bond in glyoxal, and the energy difference between the cis and the trans form of the molecule have been estimated using (7,$\text{3}\text{4}$) and (9,$\text{5}\text{4}$) Gaussian basis sets including polarization functions. The predicted energy of the cis form relative the ground state trans form was found to be substantially higher (4.9–6.3 kcal mol^?1) than the experimental value of 3.2 kcal mol^?1.