Detection of toluene diisocyanate with a coated quartz piezoelectric crystal: Part 3. Practical coatings for a humidity-corrected detector

Dithizone and tri-n-octylphosphine oxide (TOPO) were tested as coatings for quartz piezoelectric crystals to be used in a detector for touene diisocyanate (TDI). Cobalt(II) chloride and polyethylene glycol (PEG) with molecular weights of 400 and 1540 were tested for suitability as coatings for detecting humidity variations so that correction for humidity could be obtained from a two-crystal system. Sensitivities for TDI of 12 and 75 Hz ppm^?1 were found with dithizone and TOPO, respectively, between 0 and 1 ppm TDI. Cobalt chloride-coated crystals showed a sensitivity for water of 0.053 Hz ppm^?1 at 8000 ppm water and about 40 Hz ppm^?1 for TDI at the 2 ppm level. PEG-400 and PEG-1540 provided sensitivities to water of 0.038 and 0.051 Hz ppm^?1 respectively, and the response was linear over the range 9000—13 000 ppm water. All coatings showed irreversible behaviour towards TDI.     

Polysaccharides ofEremurus. X. Characteristics of the polysaccharides ofEremurus lactiflorus andE. luteus

Water-soluble polysaccharides have been isolated from two species ofEremurus — E. lactiflorus andE. luteus — with yields of 13.5% and 20.5%, respectively. They contained mainly glucose and mannose in ratios of 1:5 and 1:3.1. The polysaccharides ofE. lactiflorus were separated from a column of DEAE-cellulose. The yield of neutral fraction was 10.3%. Gel filtration of the polysaccharides on Sephadex G-200 showed their polydispersity. Homogeneous fractions were obtained by fractional precipitation with ethanol. They have been characterized with respect to monosaccharide composition, molecular weight, and IR spectra.     

Decarbonylation of N-carbazolylacetyl chloride in the friedel-crafts acylation reaction

Reaction products of N-carbazolylacetyl chloride under Friedel-Crafts reaction conditions include carbon monoxide, the reaction product from carbazole and formaldehyde (CF condensate), and carbazole. It is postulated that decarbonylation of N-carbazolylacetyl chloride involves intermediate formation of a N-carbazolylmethyl cation.     

Ungesättigte Zucker. Eine milde Sulfonat-β-Eliminierung bei Aminohexopyranosiduronat-Derivaten

Substituted 2-deoxy-2-acylamino-4-O-methanesulfonyl-hexopyranosiduronates yield, by mild alkaline mesylate (a, e)-β-elimination, the corresponding 4,5-unsaturated 4-deoxyhexopyranosiduronates VIII. This type of aminosugars proved to be the cyclic enol-ether acetal form of the 2,4-dideoxy-2-acylamino-hexos-5-ulosuronates. The structural principle of the latter can be found e.g. in neuraminic acid. These 4,5-unsaturated 4-deoxy-acylamino-hexopyranosiduronates give by reduction with NaBH₄ the corresponding 4,5-unsaturated 2,4-dideoxy-2-acylamino-hexopyranosides IX (with an endocyclic double bond on the glycosidic C atom 5). The isomeric 5,6-unsaturated 2,6-dideoxy-2-acylamino-hexopyranosides XVI (with an exocyclic double bond) are furthermore synthesized according to the method of HELFERICH [14] by elimination of a molecule of HI from the corresponding 2,6-dideoxy-2-acylamino-6-iodo-4-O-acylhexopyranoside derivatives XV. The ring stability of the two types of isomeric unsaturated hexopyranosides mentioned (bearing respectively an exo- and an endocyclic 5-enol-ether linkage) has been examined. In accordance with the stability principle of BROWN [16] – on the base of our preliminary experimental indications – the hexopyranosides with endocyclic double bond have been shown to be more stable than those with an exocyclic double bond: the latter (1) decompose slowly at 20°; (2) the α-glycosidic linkage is very easily split by dil. acetic acid at 20° within a few hours, giving 2, G-dideoxy-2-acyl-amino-D -xylo-hcxofuranos-5-ulose derivatives XX. On the other hand, the hcxopyranosides with endocyclic double bond show in the mass spectrometer, besides other fragmentations, a retro-dien decomposition. Some data on the NMR. spectra (100 and 220 MHz) of the above isomeric unsaturated acylamino-hexopyranosides (and hexopyranosiduronates, resp.) are furnished. The ORD./CD. spectra of the 4,5-unsaturated 2,4-dideoxy-2-acylamino-hexopyranosiduronates, which have two «COTTON centres», have been measured.     

Argentometric determination of iodide and cyanide using a depolarisation end-point

It has been shown that the depotarisation end-point technique, based on the phenomenon of a sudden out-of-balance current, produced by the establishment of a new redox potential at the indicator electrode in a pre-balanced circuit, can also be applied to precipitation titrations. The use of a platinum indicator electrode instead of one made of silver, and determination in very dilute solution, yield better results than those obtained using the classical potentiometric method.     

The oxonium theory in the light of an optical study of the hydrogen bond in some monovinyl ethers of glycols and polyglycols

Summary An optical investigation of some monovinyl ethers of glycols and polyglycols has indicated the presence of intermolecular hydrogen bonds in the liquid state, and this is confirmed by data derived from other phycicochemical investigations. The presence of an intermolecular hydrogen bond explains the anomalous valency of the oxygen atom of the investigated class of ethers (Its oxonium character), and also peculiarities of the properties of these ethers.     

Na-montmorillonite hydrates under ethane rich reservoirs: NPzzT and muPzzT simulations

Na-montmorillonite hydrates in presence of ethane molecules are studied by means of hybrid Monte Carlo simulations in the NP(zz)T and muP(zz)T ensembles. The NP(zz)T ensemble allows us to study the interlaminar distance as a function of water and ethane content. These data show clear plateaus for lower ethane contents and mainly for water contents consistent with the formation of a single water layer. In addition, from this ensemble the structure for some of these interlaminar compositions were analyzed. For systems containing few ethane molecules and water enough to complete a single layer, it was observed that ethane mainly situates close to the interlayer midplane and adopts a nearly parallel arrangement to the clay surface. On the other hand, the muP(zz)T ensemble allows us to determine the interlaminar distance and water-ethane content for any specific reservoir. Here, some important findings are the following: the partial exchange of water by ethane molecules that enhances for decreasing the water vapor pressure; the obtention of a practically constant interlaminar space distance as a function of the water vapor pressure; the conservation of ion solvation shells; the enhancement of the water-ethane exchange for burial conditions; and finally, the incapability for a dehydrated clay mineral to swell in a dry and rich ethane atmosphere.     

Kinetics of Addition of Alcohols to 3-Aroyl-2,4-dihydro-1H-pyrrolo[2,1-c][1,4]benzoxazine-1,2,4-triones

The kinetics of the reaction of 3-aroyl-2,4-dihydro-1H-pyrrolo[2,1-c][1,4]benzoxazine-1,2,4-triones with aliphatic alcohols in toluene at 25°C were studied by spectrophotometry. The effects of electronic and steric factors in the nucleophile and substrate were estimated by treatment of the kinetic results by the Hammett and Taft equations.     

Chemical and thermal analysis of the biopolymers in thyme (Thymus vulgaris)

Thyme (Thymus vulgaris) has been known, long time ago, for its aromatic properties. It contains essential oils and polymers such as cellulose (mixture of hemicellulose and cellulose) and lignin. The thyme, studied in this work, was gathered from the same place, in the period from November 1999 to October 2000. The chemical analysis (water, total ash, essential oils, extractive substances, cellulose, holocellulose and lignin) can be used roughly in the characterisation of the four periods that correspond to the four seasons of the year. The cellulose level was found to be more than lignin level in the wet periods (growth of the plant). The opposite was found in the dry periods. The total ash and essential oil levels were found to be high during the period of high pluviometry. The thermal decomposition of cellulose and holocellulose was found to fit well with the first-order kinetics. The activation energy, under air flow, was 185 and 196 kJ mol⁻¹ for cellulose and holocellulose, respectively. The maximum decomposition rate and thermal analysis heating rate of lignin were found to have a direct linear relationship.