The last decade has witnessed enormous growth in the asymmetric synthetic applications of dirhodium(II) carbenes
generated from diazo-precursors. Innovative construction of 'designer' catalysts has played an integral role in extending
the breadth of the synthetic cascade of non-racemic products now available through a range of cyclopropanation, C-X
insertion, aromatic cycloaddition-rearrangement, and ylide-based reaction types. This review, whilst mindful of
importance of the catalytic system, focuses primarily on the latter feature of product diversity.
Nile blue, a dye
of the phenoxazine class follows complex kinetics during its reaction with bromate in
acidic solutions. The reaction kinetics were investigated using photometric and
potentiometric techniques and a stopped flow apparatus. Under excess acid and bromate
concentration conditions, nile blue, (NB<sup>+</sup>) initially depletes very slowly.
After an induction period, a swift reaction occurs. The overall reaction is NB<sup>+</sup>
+ BrO<sub>3</sub><sup>-</sup> react to P + CH<sub>3</sub>COOH + H<sup>+</sup> + Br<sup>-</sup>,
where P is the de-ethylated N-oxide derivative of nile blue. The rapid kinetics of the
reaction of bromine direct with nile blue were also reported. A 11-step mechanism,
consistent with the overall reaction dynamics and supported by simulations, is described.
The role of various bromo- and oxybromo- species is discussed.
2-Aryl-1-methylsulfonyl-2,3-dihydroquinolin-4(1H)-ones are readily converted into the corresponding 2-aryl-3-iodo- and 2-aryl-3-bromo-1-methylsulfonyl-2,3-dihydroquinolin-4(1H)-ones using iodine in methanol and pyridinium perbromide in acetic acid, respectively. The reactions were found to be regioselective and stereoselective by 1H NMR spectroscopy, affording in all cases the 2,3-trans isomers. X-ray crystallography was also used to investigate the relative stereochemistry of these 3-halo derivatives.
The use of solid phase extraction and capillary GLC provides
the basis for selective determination of phthalate ester plasticizers in rivers
and marine water samples. Of the several solvent ratios (methanol in dichloromethane)
that were tried for selective elution of phthalate esters from the C18 solid
phase glass catridge, the 50/50 ratio, CH<sub>3</sub>OH in CH<sub>2</sub>Cl<sub>2</sub>
(v/v) gave the best result. The method was tested on river and marine water
samples that receive effluent from industries that use phthalate esters. The
rivers and marine water samples are grossly polluted as several phthalate esters,
for example, dimethyl(DMP), diethyl(DEP), dibutyl(DBP) and diethylhexyl(DEHP)
were found present at 0.03 2 306 Â± 9.4 <span lang=AF style='font-family:Symbol;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman";mso-char-type:symbol;
-family: Symbol'>m</span></span> gl<sup>-1</sup>. A study on uncontaminated water
was done to establish bank levels.
The stability constants for the inclusion complexes
of Ã?-cyclodextrin (Ã?-CD) with various adamantane derivatives
(ADA), namely the amantadinium (AM), rimantadinium (RIM), and memantinium (MEM)
cations have been determined by UV-Vis spectrophotometry. All experiments have
been performed at a pH of 1.7 and 25 </span> <span lang="EN-GB">Â°</span>
C on aqueous solutions adjusted to an ionic strength of 0.05 M (Na<sup>+</sup>,
H<sup>+</sup>)ClO<sub>4</sub>. The competitive binding method has been used
whereby methyl orange (MO) is first encapsulated by Ã?-CD and is
then substituted by ADA. It has been shown that the derivatives studied form
host-guest type complexes. The calculated stability constants, reported as log
K<sub>1</sub>, were estimated to be 3.9 Â± 0.1, 5.1 Â± 0.2 and 3.3 Â± 0.1, for
AM, RIM and MEM, respectively. The factors that govern the strength of binding
ADA with Ã?-CD have been discussed and an attempt was made to rationalise
the variation in the established stability constants for the ADA-Ã?-CD
complexes. General experimental conditions required for the determination of
the stability constants of ADA with Ã?-CD with the use of
MO as an auxiliary agent were evaluated. The optimised experimental conditions
are recommended. It has been concluded that MO, even though commonly used in
this type of study, does not meet the optimal and recommended conditions.
Methods are described for accessing the little known class of 4-alkyliminoquinoline-3-
carboxamide title compounds 4; viz., from 4-oxoquinoline-3-carboxylic acids treated
successively with thionyl chloride and amine, from 4-oxoquinoline-3-carboxylic esters
treated likewise, and from the hydrogen chloride salt of a 4-alkyliminoquinoline-3-carboxylic
ester and amine. Mechanistic aspects of the syntheses are discussed, and some
spectroscopic and chemical properties of the title compounds are presented.
This review focuses on Group 4 metallocenes and their use in the polymerisation of
<font FACE="Symbol">a</font>-olefins. A brief overview of their history as well as theories concerning the
mechanistic details of the polymerisation reaction precedes a discussion on the
design of these polymerisation catalysts. This latter section will cover what effect
metal, ligand and bridge choice has on polymerisation activity and the physical
properties of the polymer produced. A major drawback to the use of these catalysts
in industrial processes is related to the cost of their synthesis, the major problem
here being the formation of an unwanted diastereomer during the synthetic process.
The techniques employed to overcome these problems are therefore also reviewed.
Lastly, the large volume of literature dealing with these catalysts makes it difficult to
compare the polymerisation data of different catalysts and laboratories. The review
therefore contains tables that attempt to collect the details of the most important
polymerisation studies in a comparable and easy to reference manner.
Incorporation of wire mesh platinum electrodes into a standard infrared solution cell
yielded an inexpensive and easy to maintain optically transparent thin layer
electrochemical (OTTLE) cell, well suited for IR analysis of species with half-lives of
seconds to minutes. As test bed, two reactions were investigated, which are discussed
in the literature: (i) for [Ru<sub>3</sub>(CO)<sub>12</sub>] evidence was found for at least partial reversibility in
the two-electron reduction process to [Ru<sub>3</sub>(CO)<sub>11</sub>]<sup>2-</sup> , and (ii) for fac-[Re(Cl)(CO)<sub>3</sub>(4bzpy),sub>2</sub>]
(4bzpy = 4-benzoylpyridine) additional information concerning the two-step electron
reduction of the two benzoylpyridine ligands (again partially reversible) could be
The preparation of the acetone solvate of the title complex (methyl 2-(cyclohexylamino)-1-
cyclopentene-1-dithiocarboxylato)- kN, kS)carbonyltriphenyl-phosphinerhodium(I), is
described. The X-ray structure of the complex, [Rh(cacsm)(CO)(PPh3)].CH3COCH3 was
determined and a final R-value of 4.52% resulted from refinement of 5059 observed
reflections. The [Rh(cacsm)(CO)(PX3)] complexes (1), with X = phenyl (Ph), para-chlorophenyl
(p-Cl-Ph), para-methoxyphenyl (p-MeO-Ph) and cyclohexyl (Cy), undergo
oxidative addition by iodomethane, forming the Rh(III)-alkyl species (2) via an
equilibrium step, followed by the formation of the Rh(III)-acyl species (3) according to
Optimization of analytical procedure for the determination of chromium (III)/(VI)
speciation is described. A very sensitive adsorptive-catalytic stripping voltammetry
method in the presence of diethylenetriaminepentaacetic acid (DTPA) is used for
chromium speciation study in surface and ground water with in very different
The effects of various parameters (pH, ligand concentration, potential, collection
time, equilibration time,) on the response are optimized. Concentration ratio of
chromium (III)/(VI), and interferences from other metals and anions, typical for South
African waters, are considered. Results for total chromium determination are
compared with atomic absorption spectrometry (AAS) measurements.