First detection of C2H5NCO in the ISM and search of other isocyanates towards the G+0.693-0.027 molecular cloud

Context. Little is known about the chemistry of isocyanates (compounds with the functional group R-N=C=O) in the interstellar medium (ISM), as only four of them have been detected so far: isocyanate radical (NCO), isocyanic acid (HNCO), N-protonated isocyanic acid (H2NCO+), and methyl isocyanate (CH3NCO). The molecular cloud G+0.693-0.027, located in the Galactic Centre, represents an excellent candidate to search for new isocyanates since it exhibits high abundances of the simplest ones, HNCO and CH3NCO. Aims. After CH3NCO, the next most complex isocyanates are ethyl isocyanate (C2H5NCO) and vinyl isocyanate (C2H3NCO). Their detection in the ISM would enhance our understanding of the formation of these compounds in space. Methods. We have searched for C2H5NCO, H2NCO+, C2H3NCO, and cyanogen isocyanate (NCNCO) in a sensitive unbiased spectral survey carried out in the 2 mm and 7 mm radio windows using the IRAM 30m and Yebes 40m radio telescopes, respectively. Results. We have detected C2H5NCO and H2NCO+ towards G+0.693-0.027 (the former for the first time in the ISM) with molecular abundances of (4.7–7.3) × 10−11 and (1.0–1.5) × 10−11, respectively. A ratio of CH3NCO/C2H5NCO = 8 ± 1 is obtained; therefore, the relative abundance determined for HNCO:CH3NCO:C2H5NCO is 1:1/55:1/447, which implies a decrease by more than one order of magnitude, going progressively from HNCO to CH3NCO and to C2H5NCO. This is similar to what has been found for alcohols and thiols, for example, and suggests that C2H5NCO is likely formed on the surface of dust grains. In addition, we have obtained column density ratios of HNCO/NCO > 269, HNCO/H2NCO+ ∼ 2100, and C2H3NCO/C2H5NCO < 4. A comparison of the methyl/ethyl ratios for isocyanates (-NCO), alcohols (-OH), formiates (HCOO-), nitriles (-CN), and thiols (-SH) is performed and shows that ethyl derivatives may be formed more efficiently for the N-bearing molecules than for the O- and S-bearing molecules.

CO-CYCLIZATION OF ETNCO AND ME2CO AS THE RESULTS OF THEIR SELECTIVE INSERTION INTO THE NIOBIUM-CHLORINE BOND

Development of the new methods for drug production is impossible without reliance on the novel and unorthodox approaches to the synthesis of heterocyclic complexes and compounds.The method is based on the study of new aspects of the of two types of behavior of the coordinated molecules in reaction - their ability to insert into the same transition metal-halogen bond, and their ability to form the unusual heterocyclic ligands, or even molecules after leaving the complex’s coordination sphere. This will make it possible not only to synthesize the already-known compounds under milder conditions, but to also obtain new ones as products of such mixed condensation reactions. On the one hand, this opens up new possibilities for designing and performing the intraspherical "stitching" of ligands and their synthesis with high efficiency and selectivity. On the other hand, these reactions can be considered a significant contribution to the fundamental coordination chemistry in terms of illustration of the new modalities of the mutual influence of ligands, namely their ability to stimulate each other for a mutual insertion, and sheds light on the mechanisms of the intraspheric condensation. Oxadiazine derivatives, just like the derivatives of triazine we synthesized and reported previously, could become a foundation for the generation of biologically-active compounds, often containing heterocyclic fragments and frequently used for the treatment of malignant tumors. It can be expected that the developed method will find use in the synthesis of the new classes of potential antitumor compounds. We have previously found that organic isocyanate not only themselves insert into M-Hal bond, but can also activate the insertion of acetonitrile, the resulting heteromolecular chain of inserted molecules being composed of two MeNCO and one MeCN fragments. Such a structure of this complexes was confirmed be synthesis of striazine derivatives on their base. In this work was to determine optimum condition for the insertion of ethyl isocyanate with acetone into niobium-chlorine bond, as well as their subsequent mixed co-cyclization with obtaining of oxadiazine derivative.

CO-CYCLIZATION OF ETNCO AND ME2CO AS THE RESULTS OF THEIR SELECTIVE INSERTION INTO THE NIOBIUM-CHLORINE BOND

Development of the new methods for drug production is impossible without reliance on the novel and unorthodox approaches to the synthesis of heterocyclic complexes and compounds.The method is based on the study of new aspects of the of two types of behavior of the coordinated molecules in reaction - their ability to insert into the same transition metal-halogen bond, and their ability to form the unusual heterocyclic ligands, or even molecules after leaving the complex’s coordination sphere. This will make it possible not only to synthesize the already-known compounds under milder conditions, but to also obtain new ones as products of such mixed condensation reactions. On the one hand, this opens up new possibilities for designing and performing the intraspherical "stitching" of ligands and their synthesis with high efficiency and selectivity. On the other hand, these reactions can be considered a significant contribution to the fundamental coordination chemistry in terms of illustration of the new modalities of the mutual influence of ligands, namely their ability to stimulate each other for a mutual insertion, and sheds light on the mechanisms of the intraspheric condensation. Oxadiazine derivatives, just like the derivatives of triazine we synthesized and reported previously, could become a foundation for the generation of biologically-active compounds, often containing heterocyclic fragments and frequently used for the treatment of malignant tumors. It can be expected that the developed method will find use in the synthesis of the new classes of potential antitumor compounds. We have previously found that organic isocyanate not only themselves insert into M-Hal bond, but can also activate the insertion of acetonitrile, the resulting heteromolecular chain of inserted molecules being composed of two MeNCO and one MeCN fragments. Such a structure of this complexes was confirmed be synthesis of striazine derivatives on their base. In this work was to determine optimum condition for the insertion of ethyl isocyanate with acetone into niobium-chlorine bond, as well as their subsequent mixed co-cyclization with obtaining of oxadiazine derivative.

Millimeter wave spectra of ethyl isocyanate and searches for it in Orion KL and Sagittarius B2

Context. Relatively high abundances of methyl isocyanate (CH3NCO), a methyl derivative of isocyanic acid (HNCO), found in the Orion KL and Sgr B2 molecular clouds suggest that its ethyl derivative, ethyl isocyanate (CH3CH2NCO), may also be present. Aims. The aim of this work is to provide accurate experimental frequencies of ethyl isocyanate in its ground and excited vibrational states in the millimeter wave region to support searches for it in the interstellar medium. Methods. The rotational spectrum of ethyl isocyanate was recorded at room temperature from 80 to 340 GHz using the millimeter wave spectrometer in Valladolid. Assigned rotational transitions were analyzed using the S -reduced semirigid-rotor Hamiltonian. Results. More than 1100 distinct frequency lines were analyzed for the ground vibrational state of the cis conformer as well as for three vibrational satellites corresponding to successive excitation of the lowest-frequency C–N torsional mode. Newly determined rotational and centrifugal distortion constants were used for searches of spectral features of ethyl isocyanate in Orion KL and Sgr B2 clouds. Upper limits to CH3CH2NCO in these high-mass star-forming regions were obtained.

Thermoresponsive hydrogels of hydrophobically modified polyglycidol

Synthesis, swelling properties and thermoresponsive behavior of a new class of hydrogels based on high molar mass polyglycidol are presented. High molar mass polyglycidol was synthesized by coordination polymerization. Thermosensitive poly(glycidol-co-glycidyl ethyl carbamate)s were obtained via a simple chemical modification of the polyglycidol with ethyl isocyanate. Polyglycidol and poly(glycidol-co-glycidyl ethyl carbamate)s were chemically crosslinked in DMF solution using oligomeric poly(ethylene glycol)-bis-(carboxymethyl ether chloride) as crosslinking agent. The hydrogels of degree of swelling of over 1000% were obtained. Thermoresponsive properties of the networks and the swellingdeswelling behavior of hydrogels in response to cyclic changes of the temperature were studied.