ChemInform Abstract: REARRANGEMENTS OF PENTAMETHYLNAPHTHALENONIUM IONS. RELATION BETWEEN CARBONIUM ION STRUCTURE AND RATE OF THE 1,2-SHIFT OF THE METHYL GROUP

1979 ◽  
Vol 10 (32) ◽  
Author(s):  
S. V. MOROZOV ◽  
M. M. SHAKIROV ◽  
V. G. SHUBIN ◽  
V. A. KOPTYUG
Keyword(s):  
Methyl Group ◽  
Ion Structure ◽  
Carbonium Ion

scholarly journals A Kinetic and Thermodynamic Behavioral Comparison of Observable Secondary and Tertiary 2-Norbornyl Cations

1975 ◽  
Vol 53 (13) ◽  
pp. 1891-1900 ◽  
Author(s):  
R. Haseltine ◽  
N. Wong ◽  
T. S. Sorensen ◽  
A. J. Jones
Keyword(s):  
Model Systems ◽  
Suitable Model ◽  
Absolute Rate ◽  
Free Energies ◽  
Ion Structure ◽  
Hydride Shift ◽  
Carbonium Ion ◽  
Carbenium Ion ◽  
Rearrangement Processes ◽  
Rate Comparison

By analyzing various rearrangement processes, one can deduce the relative stabilities of the following 2-norbornyl cations (kcal/mol): 1,2-dimethyl, 0; 2-methyl, 1; 1-methyl, 6.5; and the parent 2-norbornyl, 8.5. Secondary 2-norbornyl cations have been assigned a "carbonium ion" structure and tertiary a "carbenium ion" structure. Using suitable model systems, an absolute rate comparison has been made of all three common rearrangement processes in the tertiary systems ("carbenium") with those already measured for the 2-norbornyl cation ("carbonium"). The activation free energies, ΔG≠, (in kcal/mol) were: Wagner–Meerwein (WM) shift: tertiary, < 4; secondary, < 4; endo-6,2-hydride shift: tertiary, 7.2; secondary, 5.8; exo-3,2-hydride shift: tertiary, 6.6; secondary, 11.4. A discussion of the structure of tertiary and secondary 2-norbornyl cations emphasizes the following points: (i) a rationalization of the rapid endo-6,2-hydride shift observed in norbornyl cations does not necessitate a protonated nortricyclene ("carbonium ion") postulate; (ii) on the basis of the results for acyclic cations and the 1,2-dimethyl-2-norbornyl cation, one would not expect to "freeze out" the WM shift in an equilibrating 2-norbornyl cation structure; (iii) the formation of nortricyclenes may be related to a partial C6—C2 bond in the ions; and (iv) the structure of the observable secondary 2-norbornyl cation probably involves partial C6—C2 bonding but, in our opinion, this does not require a symmetrical static formulation.

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.

New Amine and Aromatic Substituted Analogues of Phencyclidine: Synthesis and Determination of Acute and Chronic Pain Activities

2019 ◽  
Vol 22 (8) ◽  
pp. 570-576
Author(s):  
Maryam Shokrollahi ◽  
Marjaneh Samadizadeh ◽  
Mohsen Khalili ◽  
Seyed A. Sobhanian ◽  
Abbas Ahmadi
Keyword(s):  
Nmda Receptors ◽  
Phenyl Ring ◽  
Piperidine Ring ◽  
Methyl Group ◽  
Physiological Properties ◽  
Antinociceptive Effects ◽  
The Central Nervous System ◽  
Analgesic Activities ◽  
Compound Ii ◽  
New Compounds

Background: Phencyclidine (PCP, I) is a synthetic drug with remarkable physiological properties. PCP and its analogues exert many pharmacological activities and interact with some neurotransmitter systems in the central nervous system like particular affinity for PCP sites in NMDA receptors or dopamine uptake blocking or even both. Aim and Objective: The following research, methyl group with electron-donating and dipole moment characters was added in different positions of phenyl ring along with the substitution of benzylamine (with many pharmacological effects) instead of piperidine ring of I to produce new compounds (II-V) of this family with more analgesic activities. Materials and Methods: Analgesic activities of these new compounds were measured by tail immersion and formalin tests for acute and chronic pains, respectively. Also, the outcomes were compared with control and PCP (10 mg/kg) groups. Results: The results indicate that compounds III, IV, and V have more acute and chronic antinociceptive effects than PCP and compound II which may be concerned with more antagonizing activities of these new painkillers for the blockage of dopamine reuptake as well as high affinity for NMDA receptors PCP binding site. Conclusion: It can be concluded that the benzylamine derivative of phencyclidine with a methyl group on the benzyl position on phenyl ring (V) is a more appropriate candidate to reduce acute and chronic (thermal and chemical) pains compared to other substituted phenyl analogs (II-IV) and PCP.

The effect of 8β-methyl group on the conformation of the ring of a 2,3-disubstituted triterpenes

1974 ◽  
Vol 39 (12) ◽  
pp. 3741-3755 ◽  
Author(s):  
J. Klinot ◽  
M. Buděšínský ◽  
S. Hilgard ◽  
A. Vystrčil
Keyword(s):  
Methyl Group
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