Coated-wire organic ion-selective electrodes in titrations based on ion-pair formation: Part 2. Determination of ionic surfactants

Both cationic and anionic surfactants can be determined titrimetrically using a coated-wire electrode with a PVC membrane plasticized with 2-nitrophenyl 2-ethylhexyl ether. Cationic surfactants and other organic compounds of cationic character are titrated with sodium tetraphenylborate; for the titration of anionic compounds, cetylpyridinium bromide or 1-(ethoxycarbonyl)pentadecyl-trimethylammonium bromide (Septonex) is recommended. Characteristics of titration curves together with statistical evaluation of results are described for determinations of 15 specimens, involving pure substances as well as technical samples.     

Coated-wire organic ion-selective electrodes in titrations based on ion-pair formation: Part 3. Determination of cationic triarylmethane dyestuffs

Aqueous solutions of seven cationic triarylmethane dyestuffs can be titrated with sodium tetraphenylborate using as indicator electrode an aluminium wire coated with a PVC membrane plasticized with 2-nitrophenyl 2-ethylhexyl ether or tricresylphosphate. Titrations are possible in unbuffered and buffered media within the pH range 4–10. Characteristic titration data are given for determinations of malachite green B, seto- glaucin 0, brilliant green, fuchsine, methyl violet, crystal violet, and Victoria blue B.     

Some alkylphosphoric acid esters for use in coated-wire calcium ion-selective electrodes: Part II. Selectivities and use in potentiometric titrations

The interferences of a range of ions (including the hydrogen ion) on the potential responses of a series of coated-wire calcium-selective electrodes are reported. The extent of the interferences is discussed as a function of the composition of the PVC membranes. The use of these electrodes as end-point sensors in potentiometric titrations of calcium with EDTA is also reported.     

The coulometric titration of tetraphenylborate ion with electrogenerated silver ion and a biamperometric end-point : Application to the determination of potassium and polyethyleneglycols

Microequivalent amounts of TPB in a 40% acetone generating electrolyte were titrated with coulometrically generated silver ions. With a biamperometric endpoint, samples of 0.1–4 μeq of NaTPB were determined with a precision with 1%. The technique was applied to the determination of potassium in potassium chloride alone and in mixtures with other salts.The overall accuracy ranged from -3 to -7% for samples of 4 μeq to 1 μeq of potassium, respectively. Artificial serum samples gave somewhat discordant results, because of difficulty in removing all interfering protein. A method was developed, for the determination of 0.1–1.0 mg of PEG 600 to 4000 with excess TPB in the presence of barium ions. With reasonable care errors may be held to within 5%.     

Effect of spin-orbit coupling in para-dihalogenobenzenes on the environment-induced frequency changes in their S1 ← S0 spectra

The consequences of spin-orbit coupling in p-dihalogenobenzenes for solvent-induced shifts or S₁ ← S₀ spectral transitions, and for changes of S₁-state vibrational frequencies compared with the S₀ state, are assigned to mixing low-energy triplet states into the singlet-state system.     

N,N-Dibromobenzenesulfonamide as an analytical reagent: Determination of thiocyanate and cyanide ions in metal complexes and salts and thiosemicarbazide alone and in its metal complexes

Simple, rapid, and reproducible analytical procedures, for determining thiocyanate and cyanide ions in metal salts and complexes and thiosemicarbazide (TSC) in the free state and in its metal complexes, with the new oxidant, dibromamine-B (DBB), have been proposed. These procedures are also useful for computing the number of ligands present in the complexes. With DBB, CN⁻, and NCS⁻ ions and TSC undergo stoichiometric oxidations with 2-, 8-, and 12-electron changes per ion or molecule, respectively, in water-acetic acid medium. The reagent DBB has been prepared and characterized by elemental analyses and ir and FT-NMR-¹H and -¹³C spectral data.     

The reaction of phenylarsenazo with chromium(III)

The conditions for the reaction between phenylarsenazo (PAA) (2-[(2-arsonophenyl)azoj-7-(phenylazo)-1, 8-dihydroxynaphthalene-3,6-disulphonic acid) and chromium(III) have been studied. A blue 1:1 complex is formed at pH 2.2 on heating the reactants at 100 degrees for 15 min. It has maximum absorption at 635 nm and is stable for at least 24 hr. The molar absorptivity is 3.3 x 10(4) 1.mole(-1).cm(-1). Beer's law is obeyed in the chromium concentration range 0-1.4 mug ml . The reaction has been successfully applied to determination of chromium in alloy steel.     

Modification and optimization of a 50 MHz inductively coupled argon plasma with special reference to analyses using organic solvents

The torch and nebulizer of an existing argon ICP system were modified and the system was (re-) optimized for aqueous and organic liquids. The paper describes the design considerations and construction of(1) a new, streamlined torch including a torch base used in this study, where a demountable rather than a prealigned version of the torch was preferred;(2) a cross-flow pneumatic nebulizer with adjustable teflon capillaries including a spray chamber with flow spoiler, concentric aerosol pick-up tube, and “U” tube with unequal legs to smooth the flow of wasted liquid to the drain.The (re)-optimization of the ICP system for analysis of aqueous solutions with inorganic matter or with both inorganic and organic matter is discussed in the light of earlier work in this laboratory regarding the selection of “compromise conditions” and the choice of representative spectral lines and measurement criteria for establishing such compromise conditions. In this context the authors consider the concepts of norm temperature and “hard” and “soft” lines, as well as recent results of measurements of spatial distributions in ICPs. The authors further describe experiments aimed at the optimization of the operating conditions of an “organic ICP” using methyl isobutyl ketone (MIBK) as organic solvent. Trends of net line and background signals and signal-to-background ratios with the ICP parameters (power; outer, intermediate and carrier gas flow; observation height; liquid feed rate) are reported, and a rational choice of compromise conditions for the ICP is argued.Performance characteristics of the modified ICP system, such as detection limits, precision and interference level, achieved under compromise conditions, have been communicated in a previous report [Spectrochim. Acta36B, 1031 (1981)] to demonstrate the capabilities of the system for analysis of aqueous solutions. Detection limits in MIBK and oil diluted in MIBK are reported in the present work as an illustration of the performance of the system when used for organic liquid analysis.     

Determination of thiocyanate with aromatic halosulphonamides in acid and alkaline media

Ten organic aromatic halosulphonamides, both mono and dihalo compounds, ranging from chlorosulphonamides to iodosulphonamides, have been prepared and characterized by their infrared and NMR spectra and successfully used for determining thiocyanate in its metal salts and complexes. The proposed procedures are simple, rapid and reproducible, with an error of about +/-0.8%. These procedures are also useful for computing the number of thiocyanate ligands present in the complexes. Comparison of the present results with those from the argentometric method shows excellent agreement. The oxidation involves an 8-electron change per thiocyanate ion with the chloro and bromosulphonamides and a 6-electron change with iodosulphonamides.     

Ground-state complexes between polar solvents and 1-methylindole: the origin of the stokes'' shift in their fluorescence spectra

In iso-octane solutions containing small concentrations of the polar solvents butanol or ethyl acetate, a ground-state complex between the solute 1-methylindole and the polar solvent is formed. Previous workers aseribed the fluorescence intensity and spectral shifts of 1-methylindole in polar solvents to exciplex formation. However we show that these fluorescence properties are entirely explained in terms of ground-state complexes.     

Determination of alkylselenide compounds in air by gas chromatography—atomic absorption spectrometry

Dimethylselenide, dimethyldiselenide and diethylselenide are sampled from air by cryogenic trapping and determined by gas chromatography with electrothermal atomicabsorption spectrometric detection. Important considerations in the optimization of sensitivity and selectivity of this approach are discussed. Molecular absorption at the selenium atomic absorption wavelength is reduced by the addition of 10% hydrogen to the argon flow in the graphite oven. Detection limits down to 0.2 ng m^-3 allow the ready detection of the methyl compounds in rural air with a precision of about 10% at the nanogram level.     

Diels-alder reactions of substituted maleic anhydrides with 1-vinylcoclohexane: Stereospecific formation of a bicyclic intermediate useful for syntheses of clerodane diterpenes

The Diels-Alder reaction of 1-vinylcyclohexene with aconitic anhydride gives the adduct 5b which has the reversed stereochemistry of that predicted by Alder's endo rule. On the other hand, reactions with chloromethylmaleic anhydride and citraconic anhydride afford endo-adducts 23 and 24, respectively. Adduct 23 has the appropriate stereochemistry and functionality for the syntheses of clerodane and related diterpenes.     

Determination of thiosemicarbazide alone and in its metal complexes with arylhalosulfonamides

The behavior of 10 arylhalosulfonamides as oxidimetric analytical reagents toward thiosemicarbazide (TSC) alone or in its metal complexes has been critically examined and general procedures for its estimation have been developed. The proposed analytical techniques are simple and reproducible. These procedures are also useful for computing the number of TSC ligands present in the complexes. The oxidation involves twelve-electron change per TSC molecule with all the oxidants. The complexes have been prepared and characterized by elemental analyses and IR spectra.     

Quinoxalines and related compounds—XI: The formation of fused pyrroles by the condensation of haloazines with methylazines

2-Chloroquinoxaline reacts with a series of 2-methyl-3-substituted quinoxalines (1a-j) giving, in moderate yields, 6-substituted-pyrrolo[1,2-a: 4,5-b']-diquinoxalines (2a-j). Similar polycyclic compounds (9a-c; 11b,c; and 13b) are formed from 4-methylquinazolines (8a-c), 1-methylphthalazines (10b,c) and 2-hydroxy-4-methylpyrimidine (12b); the reaction failing with 2-methylquinazolines and 3-methylcinnolines. Polycyclic materials (17a-c) are also obtained by using chloropyrazines (15a,b) as the haloazine component. Four novel ring systems have thus been obtained; the mechanism is discussed.     

The multiphoton ionization spectrum of toluene in a supersonic free jet: internal rotation of the methyl group

The S₁← S_o electronic transitions of toluene involving also some internal rotational levels were observed for the first time in the multiphoton ionization spectrum in a supersonic jet. A large population in several low-lying internal rotational levels and a strong coupling between electronic motion and the internal rotation are suggested.     

The formation of grignard compounds—V: The reaction of iodomethane with magnesium in allyl phenyl ether. A second-order cidnp spectrum

Analysis of product formation reveals that in the reaction of iodomethane and magnesium in anyl phenyl ether ethane and 1-butane are the major side products. The latter product is formed mainly by addition of methyl radicals to the terminal CH₂ group of allyl phenyl ehter, followed by β-scission under extrusion of a phenoxy radical. This mechanism_f is confirmed by an analysis of the CIDNP spectra during the reaction; CH₃ radicals escaping from $\text{CH}{}_3\text{CH}{}_3$ pairs and adding to allyl phenyl ether give rise to a very clear example of a second order CIDNP spectrum in the product 1-butane, while polarization in $\text{CH}{}_3\text{C}{}_6\text{H}{}_5\text{O-CH-CHCH}{}_2$ pairs, formed after α-H abstraction from allyl phenyl ether, leads to net effects in the products ethane (E) and 1-methylallyl phenyl ether (A).     

The rates of deprotonation of some p-cyclopropyltoluene derivatives in search for the effect of the conformation of cyclopropyl groups on the stabi

p-Cyclopropyltoluene and 2-cyclopropylmesitylene have been prepared and the rates of base-catalyzed H-D exchange of the benzylic hydrogen atoms, para positioned with respect to the cyclopropyl group, have been compared with those of suitable model compounds. The results are in accord with earlier findings, where a cyclopropyl group exerts more stabilization to the carbanionic centres than do other alkyl groups. The present results suggest that this stabilization is independent of the conformation of the cyclopropyl group (perpendicular or bisected) with respect to the carbanionic centre.     

Infrared dichroism and molecular conformation of crystalline tetramethyldisiloxanediol

Vibrational spectra of tetramethyldisiloxanediol (TMDD) have been studied in solution and also in the solid state. Polarized IR spectra of oriented crystalline films have been recorded in the frequency range 4000–200 cm^?1. The structure of the molecules in solution has been found to be of C_2v symmetry. On the basis of the IR dichroitic data obtained for the oriented crystalline films, the molecules should have no symmetry in crystals (C₁ site symmetry) and the structure of OC₂SiOSiC₂O skeletal fragment may be described with an angle of torsion of about 70° around the (Si)O-Si bond.     

Reactions of β-substituted amines-IV: Kinetics and stereochemistry of the thermal to (r) 3-chloro-1-ethylpiperidine,and the stereo-chemical course of their reactions with nucleophiles

The rate of the thermal rearrangement of (S) 2 chloromethyl-1-ethylpyrrolidine [(S)-1a] to (R)-3-chloro-1-ethylpiperidine [(R) 2a] has been examined at three temperatures in benzene by PMR and polarimetry. The rearrangement was shown to be completely stereospecific and to obey a simple first order rate law. The calculated E_a ΔH3 and ΔS3 were 22 ± 2 $\text{kcal}\text{mole}$ (25°), 21 ± 2.5 $\text{kcal}\text{mole}$ (25°) and - 10 ± 2 e.u. (0°K) respectively. The effect of solvents having differing dielectric constants was also studied. A transition state 9'a and an ion pair intermediate 3a are suggested for the rearrangement. The stereochemical course of the reactions of (S)-1a, (R)-2a and (S)-2a with hydroxide and methoxide ions have been shown to be 100% stereospecific with an uncertainty of about 1%. The absolute configurations of all optically active reactants and products [(S)- and (R)-4a, (S)-4b (R)- and (S)-5a, (R)-5b, (S,S')-6a, (S,R')-7a and (R,R')-8a] were established by chemical correlations with known compounds or by ORD and chemical inference. The ring opening of both the primary and secondary aziridinium ion positions of 1-azonia-1-ethylbicyclo [3.1.0]hexane [(S)-3a] by nucleophiles proceeds entirely by S_N2 processes. The conversion of (R)-1-ethyl-3-hydroxypiperidine [(R)-5a] to (S)-2a. HCl with thionyl chloride in chloroform proceeds by inversion with 4.8% racemization, whereas the thermal rearrangement of (S)-1a to (R)-2a occurs with complete retention of absolute configuration.