scholarly journals Comparative effects of trifluoromethyl- and methyl-group substitutions in proline

2018 ◽  
Vol 42 (16) ◽  
pp. 13461-13470 ◽  
Author(s):  
Vladimir Kubyshkin ◽  
Stanislav Pridma ◽  
Nediljko Budisa
Keyword(s):  
Methyl Group ◽  
Methyl Substitution

What is the outcome of trifluoromethyl-/methyl-substitution in each position of the proline ring? Look inside to find out.

scholarly journals Oxidation of Methyl-Substituted Naphthalenes: Pathways in a Versatile Sphingomonas paucimobilisStrain

1998 ◽  
Vol 64 (5) ◽  
pp. 1884-1889 ◽  
Author(s):  
Tapan K. Dutta ◽  
Sergey A. Selifonov ◽  
Irwin C. Gunsalus
Keyword(s):  
Aromatic Compounds ◽  
Methyl Salicylate ◽  
Fossil Fuels ◽  
Enrichment Culture ◽  
Biological Activities ◽  
Primary Ring ◽  
Methyl Group ◽  
Methyl Substitution ◽  
Ring Fission ◽  
Single Ring

ABSTRACT Aromatic compounds with alkyl substituents are abundant in fossil fuels. These compounds become important environmental sources of soluble toxic products, developmental inhibitors, etc. principally through biological activities. To assess the effect of methyl substitution on the completeness of mineralization and accumulation of pathway products, an isolate from a phenanthrene enrichment culture,Sphingomonas paucimobilis 2322, was used. Washed cell suspensions containing cells grown on 2,6-dimethylnaphthalene in mineral medium were incubated with various mono-, di-, and trimethylnaphthalene isomers, and the products were identified and quantified by gas chromatography and mass spectrometry. The data revealed enzymes with relaxed substrate specificity that initiate metabolism either by methyl group monoxygenation or by ring dioxygenation. Congeners with a methyl group on each ring initially hydroxylate a methyl, and this is followed by conversion to a carboxyl; when there are two methyl groups on a single ring, the first reaction is aryl dioxygenation of the unsubstituted ring. Intermediates are channeled to primary ring fission via dihydrodiols to form methyl-substituted salicylates. Further evidence that there are multiple pathways comes from the fact that both phthalate and (methyl)salicylate are formed from 2-methylnaphthalene.

Triphenylpyrazine: methyl substitution to achieve deep blue AIE emitters

2019 ◽  
Vol 7 (42) ◽  
pp. 13047-13051 ◽  
Author(s):  
Haozhong Wu ◽  
Jiajie Zeng ◽  
Zeng Xu ◽  
Bing Zhang ◽  
Han Zhang ◽  
...  
Keyword(s):  
Excited State ◽  
Phenyl Group ◽  
Decay Process ◽  
Methyl Group ◽  
Methyl Substitution ◽  
State Decay ◽  
Deep Blue

Based on our deep comprehension of the unique excited state decay process of tetraphenylpyrazine derivatives, triphenylpyrazine-3-carbazole (TrPP-3C) was designed by replacing the phenyl group with a methyl group at the 3-position of pyrazine.

scholarly journals SEQUENTIAL SUBSTITUTION OF METHYL SIDE GROUP IN NAPTHOQUINONE AND ANTHRAQUINONE TO INVESTIGATE SENSITIVITY OF THE CARBONYL BAND

2017 ◽  
Vol 22 (1) ◽  
pp. 137-146
Author(s):  
Nabin Kumar Raut ◽  
Hari Prasad Lamichhane
Keyword(s):  
Aromatic Ring ◽  
The Other ◽  
Couple Mode ◽  
Side Group ◽  
Aromatic Substitution ◽  
Methyl Group ◽  
Methyl Substitution ◽  
Ring Carbon ◽  
Carbonyl Band ◽  
Sequential Addition

In this work, we have added methyl side group (s) on quinone and aromatic ring carbon positions of 1, 4-naphthoquinone (NQ) and on aromatic ring carbon positions of 1, 4-anthraquinone (AQ) in sequential increasing order to check sensitivity of the carbonyl band. In NQ, we observed that the aromatic substitution is more sensitive than the quinonic substitution. In fact, the sequential addition of CH3on the quinone ring C5 and C6 positions lead into the systematic lowering of the band and such lowering is in average of 5 cm-1 per methyl group. On the other hand, addition on the aromatic ring C7, C8, C9, and C10 positions resulted in mix effect. Indeed, they produce two types of carbonyl band, which are couple and uncouple. For further exploration of the sensitivity of the carbonyl band, we put single or two methyl group (s) on C7, C8, C9, and C10 carbon positions producing four or six NQ model molecules. We concluded that the carbonyl intense bands are more sensitive, split up, to the aromatic ring methyl substitution at C7 or C10 position. Furthermore, in AQ couple mode of C=O vibration was observed and no splitting of the band was seen on sequential CH3 addition.Journal of Institute of Science and TechnologyVolume 22, Issue 1, July 2017, Page: 137-146

Chemical reactivity of lumazine derivatives. Acid–base and redox reactions of a number of lumazines, deazalumazines, and isoalloxazines. An unusual effect of methyl substitution

1981 ◽  
Vol 59 (18) ◽  
pp. 2755-2765 ◽  
Author(s):  
Ross Stewart ◽  
R. Srinivasan ◽  
Stewart J. Gumbley
Keyword(s):  
Chemical Reactivity ◽  
Chemical Properties ◽  
Methyl Groups ◽  
Polarographic Reduction ◽  
Structural Variations ◽  
Methyl Group ◽  
Methyl Substitution ◽  
General Base ◽  
Conjugate Acid ◽  
Resonance Stabilization

Three lumazines, seven deazalumazines, and two isoalloxazines have been studied and the following chemical properties measured; equilibrium acidity (pKa), equilibrium basicity [Formula: see text] polarographic reduction potential [Formula: see text] and, where applicable, the rates of the general acid and general base catalyzed dissociation of the protons in the C-5 and C-7 methyl groups [Formula: see text] The latter quantities were determined by means of isotope exchange or iodination. Structural variations in the substrate produce compatible results in pKa and [Formula: see text] and, to lesser extents, in [Formula: see text] and in the catalytic rate data. Anomalies in the rate constants appear when a methyl group is present at C-6; it facilitates ionization of the C-5 and C-7 methyl groups, reversing the quite large effect of more distant methyl. Buttressing effects appear to be absent. The effects of methyl substitution are attributed, in part, to (a) resonance stabilization by 5- and 7-methyl groups in the reactant molecules (neutral substrate and conjugate acid), and (b) relief of steric strain in going from essentially aromatic reactants to nonplanar intermediates. The significance of the 6-methyl group in the lumazine–flavin conversion is noted.

Use of [13C-methyl]Tropinone to follow the fate of the methyl group during calystegine formation in root cultures of Solanum dulcamara (Solanaceae)

Planta Medica ◽  
2008 ◽  
Vol 74 (09) ◽  
Author(s):  
TA Bartholomeusz ◽  
R Molinié ◽  
A Roscher ◽  
AC Freydank ◽  
B Dräger ◽  
...  
Keyword(s):  
Root Cultures ◽  
Solanum Dulcamara ◽  
Methyl Group

STEROIDSTRUKTUR UND LEBERTOXIZITÄT

1967 ◽  
Vol 54 (1) ◽  
pp. 73-84 ◽  
Author(s):  
H. L. Krüskemper ◽  
G. Noell
Keyword(s):  
Alkaline Phosphatase ◽  
Liver Function ◽  
Blood Coagulation ◽  
Electrophoretic Pattern ◽  
Coagulation Factors ◽  
Blood Coagulation Factors ◽  
Methyl Group ◽  
Liver Functions ◽  
Male Subjects ◽  
Androstane Derivatives

ABSTRACT In male subjects investigations have been carried out regarding the effect of C1- and C17-methylated androstane derivatives (20 mg per day, orally, two weeks) on liver functions (parameters: activities of GPT, GOT, alkaline phosphatase and cholinesterase in serum; electrophoretic pattern; blood coagulation factors V, VII, X and prothrombin; BSP-retention). In addition to the well known hepatotropic action of 17α-alkylated C-19-steroids a quasi-axial 1α-methyl configuration (in 1α-methylandrost-2-en-17β-ol) definitely increased BSP-retention and several coagulation factors. These steroid effects decreased gradually when a methyl group was introduced in C1 equatorially (1-methylandrost-1-en-17β-ol-3-one) or quasi-equatorially (1β-methylandrost-2-en-17β-ol), the latter compound completely lacking from any influence on parameters of liver function under investigation.

A Reinvestigation of the Deceptively Simple Reaction of Toluene with ●OH, and the Fate of the Benzyl Radical. I. a Combined Thermodynamic and Kinetic Study on the Competition Between ●OH Addition and Hydrogen Abstraction Reactions.

2019 ◽  
Author(s):  
Zoi Salta ◽  
Agnie M. Kosmas ◽  
Marc E. Segovia ◽  
Martina Kieninger ◽  
Oscar Ventura ◽  
...  
Keyword(s):  
Density Functional ◽  
Room Temperature ◽  
Hydrogen Abstraction ◽  
Reaction Rates ◽  
Composite Model ◽  
Alternative Mechanism ◽  
Radical Intermediate ◽  
Experimental Conditions ◽  
Methyl Group ◽  
Benzyl Radical

This work reports density functional and composite model chemistry calculations performed on the reactions of toluene with the hydroxyl radical. Both experimentally observed H-abstraction from the methyl group and possible additions to the phenyl ring were investigated. Reaction enthalpies and heights of the barriers suggest that H-abstraction is more favorable than ●OH addition to the ring. The calculated reaction rates at room temperature and the radical-intermediate product fractions support this view. This is somehow contradictory with the fact that, under most experimental conditions, cresols are observed in a larger concentration than benzaldehyde. Since the accepted mechanism for benzaldehyde formation involves H-abstraction, a contradiction arises that begs for an explanation. In this first part of our work we give the evidences that support the preference of hydrogen abstraction over ●OH addition and suggest an alternative mechanism which shows that cresols can actually arise also from the former reaction and not only from the latter.

A Reinvestigation of the Deceptively Simple Reaction of Toluene with ●OH, and the Fate of the Benzyl Radical. I. a Combined Thermodynamic and Kinetic Study on the Competition Between ●OH Addition and Hydrogen Abstraction Reactions.

2019 ◽  
Author(s):  
Zoi Salta ◽  
Agnie M. Kosmas ◽  
Marc E. Segovia ◽  
Martina Kieninger ◽  
Oscar Ventura ◽  
...  
Keyword(s):  
Density Functional ◽  
Room Temperature ◽  
Hydrogen Abstraction ◽  
Reaction Rates ◽  
Composite Model ◽  
Alternative Mechanism ◽  
Radical Intermediate ◽  
Experimental Conditions ◽  
Methyl Group ◽  
Benzyl Radical

This work reports density functional and composite model chemistry calculations performed on the reactions of toluene with the hydroxyl radical. Both experimentally observed H-abstraction from the methyl group and possible additions to the phenyl ring were investigated. Reaction enthalpies and heights of the barriers suggest that H-abstraction is more favorable than ●OH addition to the ring. The calculated reaction rates at room temperature and the radical-intermediate product fractions support this view. This is somehow contradictory with the fact that, under most experimental conditions, cresols are observed in a larger concentration than benzaldehyde. Since the accepted mechanism for benzaldehyde formation involves H-abstraction, a contradiction arises that begs for an explanation. In this first part of our work we give the evidences that support the preference of hydrogen abstraction over ●OH addition and suggest an alternative mechanism which shows that cresols can actually arise also from the former reaction and not only from the latter.

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