Mechanisms of elimination reactions. XIII. Effect of base, solvent, and structure on product ratios in elimination reactions of some secondary tosylates

Feit, Irving N.; Saunders, William H.

doi:10.1021/ja00709a035

Cited by 11 publications

(4 citation statements)

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“…TMPDA is quite stable for the same reason as TMEDA, because of a preliminary demethylation reaction necessary to promote further degradations. However, this amine presents also some special features: ring closure, addition, and cyclic ureas (1,3-dimethyltetrahydropyrimidin-2-(1H)-one) formation do not take place in large amounts because they are in competition with Hofmann elimination 26,27 (Scheme 1). This reaction takes place only if the molecule has one labile proton at the β position of the nitrogen atom and leads to the allylamine 10 formation.…”

Section: Resultsmentioning

confidence: 99%

New Amines for CO₂ Capture. III. Effect of Alkyl Chain Length between Amine Functions on Polyamines Degradation

Lepaumier

Martin

Picq

et al. 2010

Ind. Eng. Chem. Res.

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This study examines degradation of five tertiary polyamines (di-and triamines) in the presence of CO 2 or O 2 . They were chosen to identify the impact of alkyl chain length between amine functions. Degradation of aqueous amine solutions was evaluated at 140 °C under CO 2 or air pressure (2 MPa) in stainless steel batch reactors for 15 days. At the end of the run, most degradation products were identified by gas chromatography (GC)/mass spectrometry; amounts of remaining amine and its degradation products were determined with a quantitative GC method. The main degradation mechanisms are proposed, and some structure-properties relationships are established.

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Section: Resultsmentioning

confidence: 99%

New Amines for CO₂ Capture. III. Effect of Alkyl Chain Length between Amine Functions on Polyamines Degradation

Lepaumier

Martin

Picq

et al. 2010

Ind. Eng. Chem. Res.

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“…The relative yields are indicated by lengths of the lines. er>iAro-2-Bromo-3-chlorobutane was obtained as the major product from the BrCl addition to zrazw-2-butene: bp 50-52°( 51 mm); nmr (CC14) 5.81 (m, 2 ), 8.21 (d, / = 6 Hz), 8.35 (d, / = 6.2 Hz), the latter two totaling 6 H.…”

Section: Methodsmentioning

confidence: 99%

“…A 90-g sample of I was subjected to seven brucinations, giving finally a 1.0-g sample with [ ]28346 -4.76°; the rotation increased steadily by about 0.6°/resolution. fA/-eo-2-Bromo-3-chlorobutane was prepared from the BrCl addition to c/s-2-butene: bp 50-52°(30 mm); nmr (CC14) 5.89 (m, 2 H), 8.25 (d, J = 6.5 Hz), 8.386 (d, J = 6.5 Hz), the latter two totaling 6 . A sample of the above was partially resolved by four brucination cycles to give fAreo-2-bromo-3-chlorobutane, [ ]28346 -13.0°.…”

Section: Methodsmentioning

confidence: 99%

Bridged bromine and chlorine free-radical intermediates. Free-radical halogenations of 2-halobutanes

Skell¹,

Pavlis²,

Lewis³

et al. 1973

J. Am. Chem. Soc.

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“…The reaction conditions for the reactions in alcohol solvents were as previously described. 20 Control Experiments. The absence of competition from El reactions for the butyl and pentyl bromides was demonstrated by the absence of olefins found after maintaining 2-butyl bromide in acetone or 3-pentyl bromide in DMF at the conditions used in the base-promoted reactions.…”

Section: Resultsmentioning

confidence: 99%

Olefin proportions from E2 reactions of secondary alkyl bromides. Mechanistic implications

Feit¹,

Breger²,

Capobianco³

et al. 1975

J. Am. Chem. Soc.

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The olfein proportions from E2 reactions of 2-buty1, 2-pentyl, 3-pentyl, 4-methyl-2-penty1, and 2-methyl-3-pentyl bromides with Bu4NBr in acetone, Et4NF in acetone and DMF, t-BuOK in DMF and tert-butyl alcohol, and EtOK in ethanol have been determined. When the base in not ion associated with its counterion, the kinetic transxis ratios exceed their corresponding thermodynamic ratios. The trans:cis ratio of 4-methyl-2-pentene is higher when the reactant is 2-methyl-3-pentyl bromide than when the reactant is 4-methyl-2-pentyl bromide. In aprotic solvents, an increase in the strength of the base causes an increase in transxis ratios as well as in the relative proportion of the olefin with the less alkylated double bond. From these facts, we conclude that the departing bromine atom hinders the free rotation of the alkyl group on C,; that the transition states of E2 reactions promoted by strong bases have better developed double bonds than those promoted by weak bases; and that the strength of the base is more important than the size of the base in controlling positional orientation. We suggest that the solvent type (Le., protic or aprotic) may be more important than has been generally recognized.The factors affecting olefin proportions in E2 reactions of alkyl halides (eq 1) have been extensively studied and re-viewed.' Two types of orientation are of interest. Positional orientation refers to the proportion of an olefin with a less alkylated double bond (Hofmann rule olefin) relative to an olefin with a more alkylated double bond (Saytzeff rule olefin) when more than one isomer can be formed (Le,, 1-and 2-pentene from 2-pentyl bromide). Geometrical orientation refers to the relative proportions of trans and cis isomers of the same olefin. Studies of orientation in elimination reactions have most often been conducted with hydroxide and alkoxide bases in protic solvents.* Surprisingly, a large variety of very weak bases, such as thiolate ions in alcohol solvents and halide ions in dipolar aprotic solvents, has been found to promote some elimination reactions faster than strong bases under comparable condition^.^ Winstein and Parker3d*4 have recently developed a theory to explain the ease with which weak bases can promote these reactions. Eliminations with the weak bases, according to the new theory, utilize transition states in which the base strongly interacts with C, (see eq 1) but only weakly interacts with Hp. These reactions are labeled Increasing the strength of the base causes a shift along the spectrum toward less interaction between the base and C, and greater interaction between the base and Hp. Bases as strong as alkoxide ions interact, according to this theory, exclusively with Hp, as in the classical E2 mechanism. These eliminations are labeled E2HS4 Thus, rates of elimination reactions depend on the carbon nucleophilicity as well as on the hydrogen nucleophilicity of a base.The concept of nucleophilic participation at C, by the weak bases is a modification of the merged mechanism of substitution and e l ...

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Mechanisms of elimination reactions. XIII. Effect of base, solvent, and structure on product ratios in elimination reactions of some secondary tosylates

Cited by 11 publications

References 1 publication

New Amines for CO₂ Capture. III. Effect of Alkyl Chain Length between Amine Functions on Polyamines Degradation

New Amines for CO₂ Capture. III. Effect of Alkyl Chain Length between Amine Functions on Polyamines Degradation

Bridged bromine and chlorine free-radical intermediates. Free-radical halogenations of 2-halobutanes

Olefin proportions from E2 reactions of secondary alkyl bromides. Mechanistic implications

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Mechanisms of elimination reactions. XIII. Effect of base, solvent, and structure on product ratios in elimination reactions of some secondary tosylates

Cited by 11 publications

References 1 publication

New Amines for CO2 Capture. III. Effect of Alkyl Chain Length between Amine Functions on Polyamines Degradation

New Amines for CO2 Capture. III. Effect of Alkyl Chain Length between Amine Functions on Polyamines Degradation

Bridged bromine and chlorine free-radical intermediates. Free-radical halogenations of 2-halobutanes

Olefin proportions from E2 reactions of secondary alkyl bromides. Mechanistic implications

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Product

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New Amines for CO₂ Capture. III. Effect of Alkyl Chain Length between Amine Functions on Polyamines Degradation

New Amines for CO₂ Capture. III. Effect of Alkyl Chain Length between Amine Functions on Polyamines Degradation