Oxidation of hydrocarbons. 17. Solvent and substituent effects on the oxidation of styrene derivatives by quaternary ammonium permanganates

1986 ◽  
Vol 64 (6) ◽  
pp. 1054-1059 ◽  
Author(s):  
Donald G. Lee ◽  
Keith C. Brown ◽  
Hasan Karaman
Keyword(s):  
Organic Solvents ◽  
Quaternary Ammonium ◽  
Methylene Chloride ◽  
Ion Pairs ◽  
Substituent Effects ◽  
Polar Solvents ◽  
Nonpolar Solvents ◽  
Oxidation Of Hydrocarbons ◽  
Polar Organic Solvents ◽  
Styrene Derivatives

When alkenes are oxidized by quaternary ammonium or phosphonium permanganates in polar organic solvents, such as acetone, the structures of the cations have little or no effect on the rates of reaction. In less polar solvents, such as methylene chloride or toluene, the rates of reaction are, however, dependent on the identity of the quaternary ammonium or phosphonium ions. It thus appears as if the reacting species may exist as solvent-separated ion pairs in polar solvents and as intimate ion pairs in nonpolar solvents. The rates of reaction are also very sensitive to substituent effects, a nonlinear (concave upward) Hammett plot being obtained for the oxidation of substituted β-bromo and β-methoxystyrenes. The mechanism is best visualized as proceeding by way of a continuum of transition states that can vary from electron rich to electron poor depending on the capacity of the substrate structures to accommodate either negative or positive charges.

scholarly journals SOME PROPERTIES OF A PHOTODYNAMIC PIGMENT FROM BLEPHARISMA

1953 ◽  
Vol 37 (2) ◽  
pp. 259-269 ◽  
Author(s):  
Arthur C. Giese
Keyword(s):  
Organic Solvents ◽  
Prolonged Exposure ◽  
Differential Sensitivity ◽  
Concentrated Solutions ◽  
Polar Solvents ◽  
Absorption Column ◽  
Concentrated Suspension ◽  
Alcohol Extract ◽  
Gelatin Gels ◽  
Polar Organic Solvents

1. A pigment can be extracted from Blepharisma undulans by heat treatment of a concentrated suspension of the deeply pigmented animals. 2. In the presence of this pigment, various colorless protozoans are sensitized to light and killed if exposed long enough. The protozoans show a differential sensitivity, some being much more sensitive than others. 3. Bleached colorless blepharismas are not sensitized to their own pigment even after prolonged exposure in the most concentrated solutions available. 4. Blepharisma is also less sensitive than any of the protozoans tested to such photodynamic dyes as rose bengal. 5. The pigment is not extracted from wet blepharismas by non-polar solvents, but is readily extracted into such polar organic solvents as the alcohols. 6. When the alcohol extract is dried, the amorphous residue is readily soluble in a variety of organic solvents, but not in the most non-polar. 7. The pigment is highly stable in alcohol extract and has been kept in the dark for years. 8. The pigment is bleached by light in a photooxidation. 9. Absorption maxima are found at wave lengths 5800, 5400, 4800, and 3300 A, the latter being the largest. Similar peaks are found in alcohol and water solutions, although the heights are not exactly the same. In both alcoholic and aqueous solutions pH had an effect on the absorption spectrum. Heat has little effect but illumination with intense visible light or exposure to ultraviolet light bleaches the pigment with decreases in the characteristic peaks. 10. Preliminary absorption column experiments indicate a single pigment in the alcohol extract. 11. Experiments on the migration of zoopurpurin in agar and gelatin gels indicate that it diffuses at about the same rate as eosin and is therefore probably not a large molecule.

Stereospecific 1,3-H Transfer of Indenols Proceeds via Persistent Ion-Pairs Anchored By NH···Pi Interactions

2018 ◽  
Author(s):  
David Ascough ◽  
Fernanda Duarte ◽  
Robert Paton
Keyword(s):  
Computational Analysis ◽  
Ion Pairs ◽  
Ion Pair ◽  
Hydrogen Atom Transfer ◽  
Polar Solvents ◽  
Chirality Transfer ◽  
Activation Barriers ◽  
Sense And Avoid ◽  
Phase Dynamics ◽  
Pi Interactions

The base-catalyzed rearrangement of arylindenols is a rare example of a suprafacial [1,3]-hydrogen atom transfer. The mechanism has been proposed to proceed via sequential [1,5]-sigmatropic shifts, which occur in a selective sense and avoid an achiral intermediate. A computational analysis using quantum chemistry casts serious doubt on these suggestions: these pathways have enormous activation barriers and in constrast to what is observed experimentally, they overwhelmingly favor a racemic product. Instead we propose that a suprafacial [1,3]-prototopic shift occurs in a two-step deprotonation/reprotonation sequence. This mechanism is favored by 15 kcal mol<sup>-1</sup> over that previously proposed. Most importantly, this is also consistent with stereospecificity since reprotonation occurs rapidly on the same p-face. We have used explicitly-solvated molecular dynamics studies to study the persistence and condensed-phase dynamics of the intermediate ion-pair formed in this reaction. Chirality transfer is the result of a particularly resilient contact ion-pair, held together by electrostatic attraction and a critical NH···p interaction which ensures that this species has an appreciable lifetime even in polar solvents such as DMSO and MeOH.

Analysis of natural wax from Nelumbo nucifera leaves by using polar and non-polar organic solvents

2021 ◽  
Author(s):  
Aradhya Dev Srivastav ◽  
Vireshwar Singh ◽  
Deepak Singh ◽  
Balendu Shekher Giri ◽  
Dhananjay Singh
Keyword(s):  
Organic Solvents ◽  
Nelumbo Nucifera ◽  
Polar Organic Solvents ◽  
Natural Wax

Dissolution of oxidation-cured poly(carbosilane) fiber into polar organic solvents

1997 ◽  
Vol 65 (2) ◽  
pp. 261-265 ◽  
Author(s):  
Masaki Narisawa ◽  
Satoshi Oda ◽  
Shuhei Kitano ◽  
Kiyohito Okamura
Keyword(s):  
Organic Solvents ◽  
Polar Organic Solvents

Solvent and substituent effects on rearrangement of 4-(4-X-phenyl)-2,7-dioxa-3-azabicyclo[3,3,0]oct-3-enes

1985 ◽  
Vol 50 (9) ◽  
pp. 1971-1981 ◽  
Author(s):  
Lubor Fišera ◽  
Marta Konopíková ◽  
Ladislav Štibrányi ◽  
Hans-Joachim Timpe
Keyword(s):  
Substituent Effects ◽  
Quantum Yields ◽  
Polar Solvents ◽  
Aromatic Residue ◽  
Product Ratio ◽  
Oxazoline Derivatives ◽  
Oxazine Derivatives

Preparation of the title compounds V is described. They give, on irradiation, the 2,3-dihydro-6H-1,3-oxazine derivatives VI as the main products besides the tetrahydrofuro[3,4-d]oxazoline derivatives VII. The VI to VII product ratio depends on the substituent bound to the aromatic residue. Polar solvents favour formation of the VI derivatives in the order Cl >H > CH3. In non-polar solvents the proportion of VII is increased. The quantum yields of the photoreaction vary within the limits from 0.006 to 0.04 (H >F > Cl > CH3 > OCH3).

Adsorption behaviour of neutral organic substances at the free surface of polar organic solvents

2003 ◽  
Vol 552 ◽  
pp. 77-83 ◽  
Author(s):  
J Dąbkowski ◽  
R Pruszkowska-Drachal ◽  
M Dąbkowska ◽  
Z Koczorowski ◽  
S Trasatti
Keyword(s):  
Free Surface ◽  
Organic Solvents ◽  
Organic Substances ◽  
Adsorption Behaviour ◽  
Polar Organic Solvents

Polar organic solvents accelerate the rate of DNA strand replacement reaction

The Analyst ◽  
2015 ◽  
Vol 140 (6) ◽  
pp. 2023-2028 ◽  
Author(s):  
Tianchi Zhang ◽  
Chunli Shang ◽  
Ruixue Duan ◽  
Abdul Hakeem ◽  
Zhenyu Zhang ◽  
...  
Keyword(s):  
Organic Solvents ◽  
Reaction Rate ◽  
Replacement Reaction ◽  
Polar Organic Solvents ◽  
Dna Strand

Acceleration of the reaction rate by polar organic solvents during both simple and complicated DNA strand replacement reactions is reported.

scholarly journals Regeneration of Spent Lubricant Refining Clays by Solvent Extraction

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Yan-zhen Wang ◽  
Hai-long Xu ◽  
Li Gao ◽  
Meng-meng Yan ◽  
Hong-ling Duan ◽  
...  
Keyword(s):  
Solvent Extraction ◽  
Petroleum Ether ◽  
Oil Recovery ◽  
Oil Refining ◽  
Lubricating Oil ◽  
Polar Solvents ◽  
Base Oil ◽  
Nonpolar Solvents ◽  
Total Oil ◽  
Storage Times

Step-by-step solvent extraction was used to regenerate spent clay by recovering the adsorbed oil in lubricating oil refining clay. Several polar and nonpolar solvents were tested, and petroleum ether (90–120°C) and ethanol (95 v%) were selected as the nonpolar and polar solvents, respectively. The spent clay was first extracted using petroleum ether (90–120°C) to obtain ideal oil and then extracted with a mixed solvent of petroleum ether (90–120°C) and ethanol (95 v%) two or three times to obtain nonideal oil before being extracted with ethanol and water. Finally, the clay was dried at 130°C to obtain regenerated clay. The total oil recovery can be more than 99 wt% of the adsorbed oil. The recovered ideal oil can be used as lubricating base oil. Shorter storage times for spent clay produce better regeneration results. The regenerated clay can be reused to refine the lubricating base oils.

Papain catalyzed esterification in polar organic solvents

1989 ◽  
Vol 11 (3) ◽  
pp. 173-176 ◽  
Author(s):  
Dar-Fu Tai ◽  
Shu-Ling Fu ◽  
Shu-Fen Chuang ◽  
Hsin Tsai
Keyword(s):  
Organic Solvents ◽  
Polar Organic Solvents
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