Synthesis, Chemistry, and Photochemistry of Methylcyanobutadiyne in the Context of Space Science

Application of Glaser-Hay Diyne Coupling To Constrain Nα-Amino Acid Amides via a N-N Bridge

We present the application of a Glaser-Hay diyne coupling for the synthesis of conformationally constrained N^α-amino acid amides with different diyne ring sizes. Twelve-membered rings were the smallest rings that could be prepared by this approach. We observed the formation of triethylammonium adducts in the cases of smaller (10- and 11-membered) rings. Calculation of the conformational barriers for the cyclization reactions of various ring sizes demonstrated that the formation of amino acid-derived smaller rings by this reaction is thermodynamically unfavorable.

Internal Rotation of OH Group in 4-Hydroxy-2-butynenitrile Studied by Millimeter-Wave Spectroscopy

Cyanoacetylene, HCC-CN is a ubiquitous molecule in the Universe. However, its interstellar chemistry is not well understood and its understanding requires laboratory data including rotational spectroscopy of possible products coming from a reaction with another compounds. In this study we present the first spectroscopic characterization of gauche conformation of 4-hydroxy-2-butynenitrile (HOCH₂CCCN), a formal adduct of cyanoacetylene on formaldehyde, in the frequency range up to 500 GHz. The analysis of the rotational spectrum was complicated by internal rotation of the OH group that connects two equivalent gauche configurations. The spectral assignment was aided by high-level quantum chemical calculations that were particularly useful in the interpretation of torsional-rotational part of the problem. The applied reduced-axis-system (RAS) formalism allowed fitting within experimental accuracy the lines with K _a < 18. We also present the method of search for initial global solution of torsional-rotational problem within RAS formalism. Accurate spectroscopic parameters obtained in this study provide a reliable basis for the detection of 4-hydroxy-2-butynenitrile in the interstellar medium.

Low Temperature Synthesis and Phosphorescence of Methylcyanotriacetylene

This paper reports on UV-stimulated synthesis of methylcyanotriacetylene carried out in cryogenic rare gas matrixes via coupling of smaller precursors: propyne and cyanodiacetylene. The detection was possible due to the strong visible ã ³A' → X̃ ¹A₁ phosphorescence of CH₃C₇N, discovered in the course of this work. The ensuing measurements of electronic spectroscopy revealed the formally forbidden B̃ ¹E-X̃ ¹A₁ system, as well as the allowed one Ẽ ¹A₁-X̃ ¹A₁, with origins at approximately 3.32 and 5.4 eV, respectively. It was also possible to revisit the spectroscopic characterization of cyanotriacetylene, HC₇N, formed in parallel to the title photoproduct. Spectral assignments were assisted with a density functional theory study.

One-step synthesis of conjugated enynenitriles from bromocyanoacetylene

Bromocyanoacetylene is able to provide conjugated enynenitriles stereoselectively in one step from alkynes, secondary amines and co-catalysts.

Electronic Spectroscopy of Methylcyanodiacetylene (CH3 C5 N)

The results of a study devoted to the electronic spectroscopy of gaseous, solid, and cryogenic matrix-isolated methylcyanodiacetylene (CH₃ C₅ N) are reported. UV absorption and optical phosphorescence spectra of the compound are described here for the first time, and the corresponding vibronic assignments are proposed. UV absorption, studied directly or through the excitation of phosphorescence, revealed the B˜  ¹ E--X˜  ¹ A₁ system, very weak A˜  ¹ A₂ -X˜  ¹ A₁ bands, and a strong, broad absorption feature, tentatively identified as D˜  ¹ E-X˜  ¹ A₁ . Spectral measurements were assisted by quantum chemical calculations at the DFT and ab initio (coupled cluster) levels of theory.

Infrared and Raman Spectroscopy of Methylcyanodiacetylene (CH3 C5 N)

A spectroscopic study combining IR absorption and Raman scattering is presented for methylcyanodiacetylene (CH₃ C₅ N). Gas-phase, cryogenic matrix-isolated, and pure solid-phase substance was analyzed. Out of 16 normal vibrational modes, 14 were directly observed. The analysis of the spectra was assisted by quantum chemical calculations of vibrational frequencies, IR absorption intensities, and Raman scattering activities at density functional theory and ab initio levels. Previous assignments of gas-phase IR absorption bands were revisited and extended.