摘要:

X-ray diffraction has been used to reveal precise kinetic data,in situ, for the photodimerisation reaction of a 2-benzyl-5-benzylidenecyclopentanone (BBCP) single crystal. The reaction obeys first order kinetics over a wide temperature range, is a one photon process and likely to be phonon assisted. Below a threshold temperature of ∼173 K the rate constant decreases and an Arrhenius type plot reveals that the activation energy for the reaction is ∼13.2 kJ mol−1. The rate constant is slightly reduced at higher temperatures, possibly due to increased thermal motion of the olefin bonds.

ISSN:1058-725X    

DOI:10.1080/10587259808044295

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Using atomic force microscopy(AFM), conical surface eruptions are observed on the major faces of crystals of the dialkylurethanes of5,7−dodecadiyn-1, 12−diol and α-cinnamic acid as these crystals undergo solid state reaction in the presence of air initiated by ionizing radiation and ultraviolet light, respectively. These eruptions are not observed when the irradiations are carried out in the absence of air under our experimental conditions. The eruptions formed on α-cinnamic acid are significantly smaller than those found on the polymerizing diacelylene crystals. The α-cinnamic acid single crystals were mounted on AFM slides and irradiated in the presence of bulk crystals, and the bulk conversion of the irradiated samples was estimated by proton NMR spectroscopy.

ISSN:1058-725X    

DOI:10.1080/10587259808044296

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Investigations of the photochemistry of cinnamic acid (CA) were carried out in a form of 1: 1 composite solids with dioctadecyldimethylammonium bromide (DODAB) or chloride (DODAC). UV irradiation of the composite solids with DODAB resulted in the highly selective formation of thesyn-Head-to-Head dimer, suggesting the parallel orientation of CA within the complex. Studies of X-ray diffraction, DSC, and IR spectra revealed the formation of a composite bilayer assembly showing the interaction between polar groups of CA and DODAB as well as the incorporation of CA into the alkyl regions of DODAB. On the other hand, the mixture of CA and DODAC showed less and non-selective photodimerization reaction, which could be ascribed to a disordered molecular arrangement, judging from a weak and broad endothermic peak at around reaction temperature in the DSC curve.

ISSN:1058-725X    

DOI:10.1080/10587259808044297

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In present work the molecular aggregation and interaction with metallic silver of liquid crystalline 4—pentyl—4′—cyanobiphenyl (5CB), 4—pentyl—4′—cyanophenyl pyridine (5Py), 4—pentyl—4′—cyanophenylcyclohexane (5CH), 4—octyl—4′—cyanobiphenyl (8CB), 4–8OCB) in molecular condensate films and inert matrices has been studied by low temperature reflection and transmission vibrational spectros—copy in a wide temperature range 80–330 K. The red shift of CN—stretching vibrations band was found to be due to molecular aggregates and low temperature Ag—5CB complexes formation. The factors effecting on their thermodynamic stability are con—sidered. Comprehensive IR—and UV—Vis—study of Ag—5CB film samples of different component ratio at 80K shows the exis—tence of Ag—5CB complexes due to Ag interactions with π—electrons of CN—bond of cyanobiphenyl molecules.

ISSN:1058-725X    

DOI:10.1080/10587259808044298

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The phase transition of the crystals of the complex of picric acid with l-bromo-2-aminonaphthalene(BAN) is studied by measuring the temperature variable IR absorption spectra and the differential scanning calorimetry (DSC).

ISSN:1058-725X    

DOI:10.1080/10587259808044299

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Solvent-free reactions are environmentally benign, but only if they give 100% yield. If gases react with organic crystals to produce product crystals without intervening liquid phases the yield is usually quantitative, because phase rebuilding and phase transformation are followed by crystal disintegration. That sequence of events is derived from AFM, SNOM, and X-ray data via face selective surface features. Limitations and remedies are discussed. Shrinking volumes as in linear solid-state dimerizations of interlocked 1, 1-diarylethenes leads to voids. Halogen additions of stilbene occur quantitatively. Tetra-p−bromophenylethene is also quantitatively formed. As gas-solid reactions proceed efficiently and do not usually require fine milling, they qualify for future industrial productions of almost every reaction type.

ISSN:1058-725X    

DOI:10.1080/10587259808044300

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Examples are given of organic crystals undergoing solid state reaction initiated by ionizing radiation where the properties of the product, especially surface morphology, obtained differ depending on specific experimental conditions. The authors strongly recommend that researchers using ionizing radiation for synthetic purposes specify experimental conditions used, especially the atmosphere over the sample and the radiation dosage and dose rate.

ISSN:1058-725X    

DOI:10.1080/10587259808044301

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:1058-725X    

DOI:10.1080/10587259808044254

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor