Does a methyl substituent stabilize or destabilize anions?

1978 ◽  
Vol 100 (21) ◽  
pp. 6572-6575 ◽  
Author(s):  
Addy Pross ◽  
Leo Radom
Keyword(s):  
Methyl Substituent

scholarly journals Effect of methyl substituent on the solubility of 1,4-benzoquinone derivatives in n-octanol/water system

2020 ◽  
Vol 23 (5) ◽  
pp. 142-146
Author(s):  
Siti Mariyah Ulfa ◽  
Fath Dwisari ◽  
Ade Cintyia Sally ◽  
Mohammad Farid Rahman
Keyword(s):  
Shake Flask ◽  
Water System ◽  
Insertion Reaction ◽  
Log P ◽  
Methyl Substituent ◽  
Promising Candidate ◽  
New Drug ◽  
Alkyl Bromides ◽  
Ft Ir ◽  
Uv Visible

The solubility of the compound is a crucial task for new drug design. Quinone is a promising candidate to develop as a new drug. In this research, the synthesis of 1,4-benzoquinone derivatives, that is, 2-(5-bromoamyl)-3,5-dimethyl-1,4-benzoquinone (2a) and 2-(5-bromoamyl)-5-methyl-1,4-benzoquinone (2b) were carried out by decarboxylation and insertion reaction of alkyl bromides. The product 2a and 2b are purified using SiO2 gel column chromatography and analyzed by UV-Visible, FT-IR, and NMR. The yield of 2a is 13.75%, and 2b is 4.04%. The solubility of 2a and 2b, expressed by log P, is measured in the n-octanol/water (3:7 (v/v)) system by the shake flask method. The log P of 2a and 2b are 2.99 and 1.36, respectively. It is showed that the log P of 2a is higher compared to 2b. The presence of two methyl substituents on the quinone ring of 2a supports the increase of hydrophobicity of the compound in the n-octanol/water system.

The effect of methyl and methoxy substituents on dianilines for a thermosetting polyimide system

2020 ◽  
Vol 32 (7) ◽  
pp. 801-822 ◽  
Author(s):  
John J La Scala ◽  
Greg Yandek ◽  
Jason Lamb ◽  
Craig M Paquette ◽  
William S Eck ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Molecular Weight ◽  
Glass Transition ◽  
Elevated Temperature ◽  
Methyl Substituent ◽  
Glass Transition Temperatures ◽  
High Performing ◽  
Methoxy Substituent ◽  
Acidic Conditions ◽  
Thermal Stability Of

4,4′-Methylenedianiline (MDA) is widely used in high-temperature polyimide resins, including polymerization of monomer reactants-15. The toxicity of MDA significantly limits the manufacturability using this resin. Modifying the substitution and electronics of MDA could allow for the reduction of toxicity while maintaining the high-performing properties of the materials derived from the modified MDA. The addition of a single methyl substituent, methoxy substituent, location of these substituents, and location of the amine relative to the phenolic bridge were modified as were other non-aniline diamines. Various anilines were condensed with paraformaldehyde under acidic conditions to yield dianilines. These dianilines and diamines were reacted with nadic anhydride and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride in methanol to form the polyamic acid oligomers and heated at elevated temperature to form polyimide oligomers. It was found that the molecular weight of the oligomers derived from MDA alternatives was generally lower than that of MDA oligomers resulting in lower glass transition temperatures ( T gs) and degradation temperatures. Additionally, methoxy substituents further reduce the T g of the polymers versus methyl substituents and reduce the thermal stability of the resin. Methyl-substituted alternatives produced polyimides with similar T gs and degradation temperatures. The toxicity of the MDA alternatives was examined. Although a few were identified with reduced toxicities, the alternatives with properties similar to that of MDA also had high toxicities.

Directing Bromination of Piperazine-2,5-diones

1995 ◽  
Vol 48 (7) ◽  
pp. 1379 ◽  
Author(s):  
TW Badran ◽  
CLL Chai ◽  
CJ Easton ◽  
JB Harper ◽  
DM Page
Keyword(s):  
Free Radical ◽  
Methyl Substituent ◽  
Radical Bromination ◽  
Acetyl Group

From intermolecular and intramolecular competition experiments, it has been established that, by comparison with an N-methyl substituent, an N-acetyl group deactivates glycine residues in piperazine-2,5-diones towards free-radical bromination. Combined with the ease of introduction and removal of N-acetyl substituents, the deactivating effect provides a method for regiocontrolled functionalization of these compounds.

Comparative kinetics of cytosine nucleosides. Influence of a 6-methyl substituent on degradation rates and pathways in aqueous buffers

1972 ◽  
Vol 15 (12) ◽  
pp. 1207-1214 ◽  
Author(s):  
Robert E. Notari ◽  
Donald T. Witiak ◽  
Joyce L. DeYoung ◽  
Ai Jeng Lin
Keyword(s):  
Methyl Substituent ◽  
Degradation Rates ◽  
Kinetics Of

Influence of 2′-Fluoro versus 2′-O-Methyl Substituent on the Sugar Puckering of 4′-C-Aminomethyluridine

2013 ◽  
Vol 78 (19) ◽  
pp. 9956-9962 ◽  
Author(s):  
Kiran R. Gore ◽  
S. Harikrishna ◽  
P. I. Pradeepkumar
Keyword(s):  
Methyl Substituent ◽  
Sugar Puckering

scholarly journals The effect of orientation of the lateral methyl substituent on the mesophase behaviour of 4-alkoxyphenylazo aryl benzoates

2016 ◽  
Vol 43 (12) ◽  
pp. 1831-1845 ◽  
Author(s):  
Magdi M. Naoum ◽  
Abdelgawad A. Fahmi ◽  
Amira H. Abaza ◽  
Gamal R. Saad
Keyword(s):  
Methyl Substituent
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