A reinvestigation of the vapor phase bromination of 2-bromobutane

1984 ◽  
Vol 62 (11) ◽  
pp. 2310-2316 ◽  
Author(s):  
Dennis D. Tanner ◽  
Tomoki C. S. Ruo ◽  
Yoshio Kosugi ◽  
Alan Potter
Keyword(s):  
Vapor Phase ◽  
Thermal Instability ◽  
Addition Reaction ◽  
Bromine Atom ◽  
Solution Phase ◽  
Reaction Schemes

The solution phase photobromination of 2-bromobutane yields 2,2-dibromobutane, meso-2,3-dibromobutane, dl-2,3-dibromobutane, small amounts of 1,2-dibromobutane, and 2,2,3-tribromobutane. However, in the corresponding vapor phase bromination these products appear along with other polybrominated products. The yield of these polybromides increases with temperature. The increase in yield of the polyhalogenated materials is rationalized by considering the thermal instability of the β-bromoalkyl radical, which eliminates a bromine atom to form the corresponding alkene. It is demonstrated that in the vapor phase allylic bromination competes successfully with bromine addition. Reaction schemes are suggested to explain the formation of polybromides. An explanation is also offered for the discrepancy between these results and those of previously reported vapor phase work.

The relative rates of bromination of cyclohexane and cyclopentane with molecular bromine. Comparison of the reactions in solution and in vapor phase

1981 ◽  
Vol 59 (9) ◽  
pp. 1368-1374 ◽  
Author(s):  
Dennis D. Tanner ◽  
Tomoki C-S. Ruo ◽  
Hideki Takiguchi ◽  
Andre Guillaume
Keyword(s):  
Vapor Phase ◽  
Hydrogen Bromide ◽  
Bromine Atom ◽  
Relative Rate ◽  
Solution Phase ◽  
Molecular Bromine ◽  
Transfer Rates ◽  
Relative Rate Constants ◽  
Halogenated Alkanes ◽  
Relative Transfer

The relative rates of transfer of the cyclopentyl radical with molecular bromine and hydrogen bromide (k2′/k−1′) and with hydrogen tribromide and hydrogen bromide (k3′/k−1′) have been determined. The relative transfer rates are compared with the analogous values previously reported for the reactions of cyclohexyl radicals (k2/k−1 and k3/k−1). Utilizing the values of k2′/k−1 and k2/k−1 the competitive vapor phase rates of bromine atom abstraction of hydrogen from the two substrates could be obtained. An expression using a combination of the five sets of relative rate constants was used to determine the effect of competitive cage reversal which occurs in the solution phase bromination of the two substrate radicals with caged hydrogen bromide. For two structurally similar radicals, cage reversal (internal return) was found to affect the relative rates of bromination by 30%, while the relative transfer rates, although differing each by a factor of two, fortuitously nearly cancel each other's effect.The effect of both internal and external reversal reactions on the relative rates of bromination of structurally dissimilar substrates, halogenated alkanes and their parent hydrocarbons, is discussed.

Vapor-phase and solution-phase UV spectroscopic studies of η5-pentadienyl derivatives of iron and ruthenium

1998 ◽  
Vol 563 (1-2) ◽  
pp. 209-217 ◽  
Author(s):  
Sergey Yu Ketkov ◽  
Richard D Ernst ◽  
Lothar Stahl ◽  
Wimonrat Trakarnpruk
Keyword(s):  
Vapor Phase ◽  
Spectroscopic Studies ◽  
Solution Phase ◽  
Derivatives Of

Free radical hydrobromination of propargyl bromide and bromoallene

1969 ◽  
Vol 47 (17) ◽  
pp. 3153-3165 ◽  
Author(s):  
Karl R. Kopecky ◽  
Shima Grover
Keyword(s):  
Free Radical ◽  
Kinetic Study ◽  
Addition Reaction ◽  
Hydrogen Bromide ◽  
Bromine Atom ◽  
Liquid Hydrogen ◽  
Major Product ◽  
Propargyl Bromide ◽  
Solvent Cage ◽  
Ether Solution

Rearrangement is observed in the free-radical hydrobromination of propargyl bromide. Between −20 and +30 °C in n-pentane or ether solution, 1,2-dibromopropene is the major product. A detailed stereochemical and kinetic study of the reaction indicates that the 1,2-dibromopropene is formed via bromoallene which results from the loss of a bromine atom from the first formed 1,3-dibromo-2-propenyl radical. Only 1/3 to 1/2 of the bromoallene diffuses away from its bromine atom partner. The remainder of the bromoallene recombines within the solvent cage with its bromine atom partner at a rate which is competitive with its rate of rotation with respect to the bromine atom. When the free radical hydrobromination of propargyl bromide is carried out at −78° in liquid hydrogen bromide, the 1,3-dibromo-2-propenyl radical can be trapped to a large extent by the hydrogen bromide to form cis-1,3-dibromopropene. The stereochemistry of this addition reaction >99% trans. A small amount of 1,2-dibromopropene which is 77% trans is also formed. Under the same conditions a 3:1 mixture of 1,2- and 1,3-dibromopropenes is produced from bromoallene. The 1,3-dibromopropene produced from bromoallene is >95% cis, while the 1,2-dibromopropene consists of a 49:51 cis:trans mixture of isomers.

An investigation of the photodecomposition of N-bromosuccinimide; the generation and reactivity of succinimidyl radical

1979 ◽  
Vol 57 (15) ◽  
pp. 1967-1976 ◽  
Author(s):  
Fu-Lung Lu ◽  
Yousry M. A. Naguib ◽  
Masayuki Kitadani ◽  
Yuan L. Chow
Keyword(s):  
Double Bond ◽  
Low Temperature ◽  
Ethylene Oxide ◽  
Addition Reaction ◽  
Bromine Atom ◽  
Electronic Configuration ◽  
High Concentration ◽  
Carbon Double Bond ◽  
Acetonitrile Solutions

The photolysis of acetonitrile solutions of N-bromosuccinimide (NBS) in the presence of ethylene oxide and an excess of olefins or benzene in the −30 ∼ 20 °C range was shown to generate the succinimidyl radical in competition with the bromine atom reactions. The succinimidyl radical preferentially attacked a π bond to give 1-succinimidyl-2-bromoalkanes, rather than abstracting alkyl hydrogens. Allylic bromination also occurred and competed with the 1,2-addition. Formation of 3-bromocyclohexene in the presence of cyclohexene at 10–20 °C could be effectively reduced at lower temperatures or in the presence of a high concentration of ethylene oxide; the 1,2-addition process was favored at low temperature but surprisingly not facilitated significantly in the presence of ethylene oxide. The primary adducts from benzene readily eliminate HBr to give N-phenylsuccinimide. The attack of a bromine atom on a carbon–carbon double bond may become an important step in the 0 ∼ −30 °C range. The ease of the addition reaction suggests that this succinimidyl radical may have a Σ electronic configuration.

Planar defects in ordered (Ga,In)P

1988 ◽  
Vol 46 ◽  
pp. 902-903
Author(s):  
S. McKernan ◽  
C. B. Carter ◽  
D. Bour ◽  
J. R. Shealy
Keyword(s):  
Electron Diffraction ◽  
Vapor Phase ◽  
Growth Direction ◽  
High Density ◽  
Ordered Structure ◽  
Planar Defects ◽  
Diffraction Patterns ◽  
Ternary Semiconductors ◽  
Anion Species ◽  
Metallic Vapor

The growth of ternary III-V semiconductors by organo-metallic vapor phase epitaxy (OMVPE) is widely practiced. It has been generally assumed that the resulting structure is the same as that of the corresponding binary semiconductors, but with the two different cation or anion species randomly distributed on their appropriate sublattice sites. Recently several different ternary semiconductors including AlxGa1-xAs, Gaxln-1-xAs and Gaxln1-xP1-6 have been observed in ordered states. A common feature of these ordered compounds is that they contain a relatively high density of defects. This is evident in electron diffraction patterns from these materials where streaks, which are typically parallel to the growth direction, are associated with the extra reflections arising from the ordering. However, where the (Ga,ln)P epilayer is reasonably well ordered the streaking is extremely faint, and the intensity of the ordered spot at 1/2(111) is much greater than that at 1/2(111). In these cases it is possible to image relatively clearly many of the defects found in the ordered structure.

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