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61.
The monohydroboration of caryophyllene with dicyclohexylborane followed by oxidation brought about the participation of the (E)-trisubstituted double bond in preference to the exocyclic double bond during hydroboration to the corresponding unsaturated alcohol. This alcohol gave the corresponding ketone by oxidation. Isocaryophyllene under similar conditions provided the unsaturated alcohol as the major product, wherein the participation of the exocyclic double bond took place during hydroboration. Our attempts to achieve cyclic hydroboration with caryophyllene or isocaryophyllene using thexylborane resulted in the formation of the corresponding unsaturated alcohol. We achieved partial regioselective reduction of caryophyllene and isocaryphyllene with diimide to produce the corresponding dihydroderivative. 相似文献
62.
The soluble deep blue complex of iron(II) with o-mercaptobenzoic acid in aqueous pyridine medium (pH 6.4-7.4) can be titrated with EDTA at room temperature with a sharp colour change from blue to light yellow. o-Mercaptobenzoic acid forms a 2:1 complex with iron(II), maximum absorption at 600 nm. Its stability constant was found to be log K = 7.7. With iron(III), a transient blue colour is first formed which soon becomes colourless and then on the addition of excess of reagent, the deep blue complex is formed on reduction of the iron(III). Iron can be titrated in the presence of copper, if the latter is masked with sodium thiosulphate. Cobalt and nickel interfere. Common anions such as chloride, tartrate, phosphate, oxalate, citrate and acetate have no interference. 相似文献
63.
[reaction in text] Protected pyridylhydrazine derivatives were prepared in a one-step palladium-catalyzed amination reaction using chelating phosphine ligands. 2-Pyridyl chlorides, bromides, and triflates were effective electrophiles in these reactions. Di-tert-butyl hydrazodiformate was an excellent hydrazine substrate, and the resulting products were deprotected under mild conditions. Catalytic amination provides a direct route to protected bifunctional hydrazinopyridine linkers that are suitable for metal-bioconjugate syntheses. 相似文献
64.
Summary A method has been developed for the fluorimetric determination of boric acid, which gives a blue fluorescence with resacetophenone in sulphuric acid or phosphoric acid medium. The method has the advantage that the reaction does not require much time, because the fluorescence intensity reaches its maximum immediately after mixing the reagents and does not also decrease with time. The intensity of fluorescence can be measured with a fluorimeter and the amount of boric acid determined from a calibration curve. 相似文献
65.
Rao CN Kulkarni GU Thomas PJ Edwards PP 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(1):28-35
Properties of materials determined by their size are indeed fascinating and form the basis of the emerging area of nanoscience. In this article, we examine the size dependent electronic structure and properties of nanocrystals of semiconductors and metals to illustrate this aspect. We then discuss the chemical reactivity of metal nanocrystals which is strongly dependent on the size not only because of the large surface area but also a result of the significantly different electronic structure of the small nanocrystals. Nanoscale catalysis of gold exemplifies this feature. Size also plays a role in the assembly of nanocrystals into crystalline arrays. While we owe the beginnings of size-dependent chemistry to the early studies of colloids, recent findings have added a new dimension to the subject. 相似文献
66.
H. Surya Prakash Rao S. Senthilkumar K. Gopu Shaik Rafi 《Chemistry of Heterocyclic Compounds》2007,43(3):292-297
The microwave-mediated reaction of 4-aryl-4-oxobutanoic acids with benzylamines furnished 1-arylmethyl-3-[(E)-1-arylmethylidene]-5-phenyl-2,3-dihydro-1H-pyrrolones.
This result is in contract to the earlier report on this reaction conducted under neat conditions. Structures for the products
were assigned on the basis of spectral data and confirmed by independent synthesis.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 368–373, March, 2007. 相似文献
67.
The use of 2-nitrodiphenylamine as a reversible indicator has been investigated in the titration of iron(II) with cerium(IV) sulphate, potassium dichromate and sodium vanadate in sulphuric acid media. Accurate results can be obtained with cerium(IV) sulphate in 0.5–5.0 M acid, with potassium dichromate in 5.0–7.0 M acid, and with sodium vanadate in 5.0–7.5 M acid. With cerium(IV) sulphate the titrations are preferably conducted in 2.0 M sulphuric acid or in a 1.0 M. sulphuric acid-1.0 M pechloric acid medium. Tungstic acid, acetic acid, arsenic(III) and manganese(II) do not interfere. In titrations of iron(II) with dichromate and vanadate, the colour changes at the end-point are much more vivid with 2-nitrodiphenylamine than with ferroin. 相似文献
68.
T.?L.?Shanker Rao K.?N.?Lad A.?PratapEmail author 《Journal of Thermal Analysis and Calorimetry》2004,78(3):769-774
The crystallization kinetics of amorphous Cu50Ti50 has been studied using differential scanning calorimetry (DSC) under non-isothermal conditions. The curves at different linear heating rates (2, 4, 8 and 16 K min–1) show sharp crystallization peaks. The crystallization peak shifts to higher temperatures with increasing heating rate. The Kissingers method of analysis of the shift in the transformation peak is applied to evaluate the activation energy (E
c). The KJMA formalism, which is basically developed for isothermal experiments, is also used to obtain E
c and the Avrami parameter (n).The DSC data have been analysed in terms of kinetic parameters, viz. activation energy (E
c), Avrami exponent (n) and frequency factor K
0 using three different theoretical models. It is observed that the activation energy values derived from KJMA approach and modified Kissinger equation agree fairly well with each other. The activation energy values obtained from normal Kissinger method, and Gao and Wang expression underestimate the activation energy.The financial support provided by All India Council for Technical Education (AICTE), New Delhi (Govt. of India) is gratefully acknowledged. 相似文献
69.
V. Bhagavathy M. L. P. Reddy T. Prasada Rao A. D. Damodaran 《Journal of Radioanalytical and Nuclear Chemistry》1991,149(1):35-40
A method is described for the simultaneous multielement determination of yttrium and lanthanides at microgram level. This is based on the preconcentration of these lanthanides on to 1-(2-pyridylazo)-2-naphthol (PAN) modified naphthalene. The optimal conditions for quantitative preconcentration viz., pH, amount of PAN modified naphthalene, time of stirring and aqueous phase volume were systematically evaluated. The quantitation of lanthanides was carried out by energy dispersive X-ray fluorescence analyzer, employing241Am annular source, via their characteristic K X-rays. The developed procedure gave reliable results in the analysis of xenotime samples. 相似文献
70.
J. C. Evans K. R. N. Rao S. K. Jackson C. C. Rowlands M. D. Barratt 《Journal of separation science》1985,8(12):829-830
Radicals generated in linoleic acid and deuterated linoleic acid have been trapped by the spin trap 2-methyl-2-nitroso-propane (MNP) and identified by electron spin resonance (ESR) and ENDOR spectroscopy. The formation of two distinct secondary alkyl radical adducts (one conjugated, the other non-conjugated, as shown by their UV absorption spectra) was demonstrated by 11, 11-dideuterio-9-cis-12-cis-linoleic acid using HPLC and ESR spectroscopy. 相似文献