An NMR and ab Initio Quantum Chemical Study of Acid−Base Equilibria for Conformationally Constrained Acidic α-Amino Acids in Aqueous Solution

2001 ◽  
Vol 123 (9) ◽  
pp. 2003-2006 ◽  
Author(s):  
Peter Aadal Nielsen ◽  
Jerzy W. Jaroszewski ◽  
Per-Ola Norrby ◽  
Tommy Liljefors
Keyword(s):  
Aqueous Solution ◽  
Amino Acids ◽  
Ab Initio ◽  
Quantum Chemical ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Acid Base ◽  
Conformationally Constrained

Spectrophotometric and quantum-chemical study of acid-base and complexing properties of (±)-taxifolin in aqueous solution

2017 ◽  
Vol 23 (5) ◽  
Author(s):  
Maxim A. Lutoshkin ◽  
Boris N. Kuznetsov ◽  
Vladimir A. Levdansky
Keyword(s):  
Aqueous Solution ◽  
Quantum Chemical ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Acid Base ◽  
Equilibrium Processes ◽  
Complexing Properties ◽  
Aqueous Complexation ◽  
Base Properties

AbstractThis study reports the acid-base properties of taxifolin (Tf) in HCl media and aqueous complexation with Ni(II). The equilibrium processes was investigated using a spectrophotometric technique and

AB initio quantum chemical study of the reaction mechanism of ethynide ion formation in the C2H2/MOH/DMSO system (M = Li, Na, K)

2009 ◽  
Vol 50 (1) ◽  
pp. 27-33 ◽  
Author(s):  
E. Yu. Larionova ◽  
N. M. Vitkovskaya ◽  
V. B. Kobychev ◽  
N. V. Kaempf ◽  
A. D. Skitnevskaya ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Ab Initio ◽  
Quantum Chemical ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Ion Formation ◽  
Dmso System

Quantum chemical study on the formation of isopropyl cyanide and its linear isomer in the interstellar medium

2020 ◽  
pp. 1-11
Author(s):  
Keshav Kumar Singh ◽  
Poonam Tandon ◽  
Alka Misra ◽  
Shivani ◽  
Manisha Yadav ◽  
...  
Keyword(s):  
Amino Acids ◽  
Interstellar Medium ◽  
Gas Phase ◽  
Quantum Chemical ◽  
Density Functional ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Dark Cloud ◽  
Water Ice ◽  
Hydrocarbon Radicals

Abstract The formation mechanism of linear and isopropyl cyanide (hereafter n-PrCN and i-PrCN, respectively) in the interstellar medium (ISM) has been proposed from the reaction between some previously detected small cyanides/cyanide radicals and hydrocarbons/hydrocarbon radicals. n-PrCN and i-PrCN are nitriles therefore, they can be precursors of amino acids via Strecker synthesis. The chemistry of i-PrCN is especially important since it is the first and only branched molecule in ISM, hence, it could be a precursor of branched amino acids such as leucine, isoleucine, etc. Therefore, both n-PrCN and i-PrCN have significant astrobiological importance. To study the formation of n-PrCN and i-PrCN in ISM, quantum chemical calculations have been performed using density functional theory at the MP2/6-311++G(2d,p)//M062X/6-311+G(2d,p) level. All the proposed reactions have been studied in the gas phase and the interstellar water ice. It is found that reactions of small cyanide with hydrocarbon radicals result in the formation of either large cyanide radicals or ethyl and vinyl cyanide, both of which are very important prebiotic interstellar species. They subsequently react with the radicals CH2 and CH3 to yield n-PrCN and i-PrCN. The proposed reactions are efficient in the hot cores of SgrB2 (N) (where both n-PrCN and i-PrCN were detected) due to either being barrierless or due to the presence of a permeable entrance barrier. However, the formation of n-PrCN and i-PrCN from the ethyl and vinyl cyanide always has an entrance barrier impermeable in the dark cloud; therefore, our proposed pathways are inefficient in the deep regions of molecular clouds. It is also observed that ethyl and vinyl cyanide serve as direct precursors to n-PrCN and i-PrCN and their abundance in ISM is directly related to the abundance of both isomers of propyl cyanide in ISM. In all the cases, reactions in the ice have smaller barriers compared to their gas-phase counterparts.

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