ChemInform Abstract: SUBSTITUENT EFFECTS IN FREE-RADICAL REACTIONS. A STUDY OF 4-SUBSTITUTED 3-CYANOBENZYL FREE RADICALS

1978 ◽  
Vol 9 (21) ◽  
Author(s):  
T. H. FISHER ◽  
A. W. MEIERHOEFER
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Substituent Effects ◽  
Radical Reactions ◽  
Free Radical Reactions

Reaction of Chloral with 1,4-Polyisoprene

1963 ◽  
Vol 36 (4) ◽  
pp. 1056-1058
Author(s):  
Christian Pinazzi ◽  
Rene Pautrat ◽  
Roland Cheritat
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Nitrogen Atmosphere ◽  
Radical Reactions ◽  
Molar Ratio ◽  
Free Radical Reactions ◽  
Main Fraction ◽  
Ionic Reactions ◽  
Macromolecular Substance ◽  
Chloroform Methanol

Abstract The cis-1,4-polyisoprenes are composed of 2-methyl-2-butene units, the double bonds of which must be favorable to the addition of strongly electrophylic reagents such as certain aldehydes. Chloral is of this type and its ionic reactions with various simple olefins has been described. We found it worth while to transpose these results to polyisoprenic macromolecules, either natural or synthetic. The ionic reactions generally create less modifications of the chain, such as fission or crosslinking, than would result from free radical reactions. Also, if the formation of free radicals is avoided, the possible fixation of chloral on the halogen carrying carbon (group —CCl2—CHO) becomes very unlikely. Pure anhydrous chloral is used as the reagent. A solution of 2% cis-1,4-polyisoprene (natural) in cyclohexane or decalin (free of peroxides) is heated under a nitrogen atmosphere with the reagent and in presence of a catalyst such as AlCl3 or BF3 at a concentration of 1–3% relative to the polyisoprene. The macromolecular product obtained is then subjected to a fractionation by the chloroform-methanol combination. After purification and desolvation of the main fraction an elemental analysis is made and the level of fixation n calculated based on the chlorine content. Table 1 relates some of the results obtained by using AlCl3 or BF3. In the absence of catalyst (Figure 1, A) the level of fixation is low: n=4 and therefore the nature of the reaction remains uncertain. In the presence of AlCl3 or of BF3, n increases rapidly in function of the temperature and of the relative molar concentration of the reagents, as shown by the curves B and C of Figure 1. The highest level of fixation obtained in these experiments is n=22. Figure 2 demonstrates this limit which is reached beyond the molar ratio of m=4, in the presence of AlCl3 (3%). Table 2 shows the particular action of AlCl3 which among all the catalysts tested proves to be as effective as BF3 without yielding any notable crosslinking of the macromolecular substance.

Acyclic Stereocontrol of Free Radical Reactions Involving Alkyl 2-(1-Hydroxyalkyl)propenoates

1994 ◽  
Vol 47 (12) ◽  
pp. 2187 ◽  
Author(s):  
FW Eastwood ◽  
RD Mifsud ◽  
P Perlmutter
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Simple Model ◽  
Radical Reactions ◽  
Temperature Dependent ◽  
Free Radical Reactions ◽  
Butyl Radical ◽  
Acyclic Stereocontrol ◽  
Derivatives Of

The addition of cyclohexyl and t-butyl free radicals to silylated derivatives of alkyl 2-(1-hydroxyalkyl) propenoates was found to be stereoselective . In the case of the cyclohexyl radical the stereoselectivity was dependent upon the conditions used to generate the free radical and to quench the intermediate. Stereoselectivity in additions of the t-butyl radical was found to be temperature-dependent. In all cases stereoselectivity increased as the steric bulk of the group attached to the carbinol oxygen increased. A simple model which accounts for the stereoselectivity is proposed.

Free Radicals: Free Radical Reactions in Two Dimensions: A Case Study on Photochlorination of Graphene (Small 8/2013)

Small ◽  
2013 ◽  
Vol 9 (8) ◽  
pp. 1387-1387
Author(s):  
Lin Zhou ◽  
Lushan Zhou ◽  
Mingmei Yang ◽  
Di Wu ◽  
Lei Liao ◽  
...  
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Two Dimensions ◽  
Radical Reactions ◽  
Free Radical Reactions
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