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Original Experimental Approach for Assessing Transport Fuel Stability
Published on: October 21, 2016
ガス相におけるアルキル水酸化物 (ROOH) の塩基媒介分解の直接的な証拠
Stephen J Blanksby1, G Barney Ellison, Veronica M Bierbaum
1Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA.
Journal of the American Chemical Society
|March 28, 2002
まとめ
フッ化物イオン (F-) とメチル水酸化物 (CH3OOH) の間の反応は急速であり,水酸化物イオン (HO-) とホルムアルデヒド (CH2O) が形成されます. この塩基媒介分解機構は,他のアルキル水酸化物にも適用できる.
科学分野:
- 化学動力学 化学動力学
- ガス相イオン化学
- 反応メカニズム 反応メカニズム
背景:
- アルキル水酸化物は,大気および生物学的システムにおいて重要である.
- それらの分解経路を理解することは,様々な化学プロセスにとって極めて重要です.
研究 の 目的:
- メチル水酸化物とフッ化物イオンのガス相反応機構を調査する.
- 主要な製品の形成経路を解明し,反応機構を特定する.
主な方法:
- タンデムフローアfterglow選択イオンフローチューブ装置を使用しました.
- イソトープのラベル付けと計算研究を行いました.
- より大きなアルキル水酸化物による反応を研究した.
主要な成果:
- F−とCH3OOHの反応は迅速で,HO−+CH2O+HFが主要な産物チャネル (85%) である.
- アルファ水素を含むアルキル水素酸化物に適用できるHO-形成のための協調的な除去機構が特定されました.
- 逆反応CH3OO-+HFも効率的に進行する.
結論:
- 特定されたメカニズムは,アルキル水酸化物 (alkyl hydroperoxides) のガス相塩基媒介分解を表しています.
- このメカニズムは,溶液と生化学反応に大きな影響を及ぼす可能性があります.
- 逆反応では,アニオンの新しい中性触媒分解が観察されました.
関連する概念動画
Radical Anti-Markovnikov Addition to Alkenes: Mechanism
The reaction of hydrogen bromide with alkenes in the presence of hydroperoxides or peroxides proceeds via anti-Markovnikov addition. The radical chain reaction comprises initiation, propagation, and termination steps.
The mechanism starts with chain initiation, which involves two steps. In the first chain initiation step, a weak peroxide bond is homolytically cleaved upon mild heating to form two alkoxy radicals. In the second initiation step, a hydrogen atom is abstracted by the alkoxy radical...
The mechanism starts with chain initiation, which involves two steps. In the first chain initiation step, a weak peroxide bond is homolytically cleaved upon mild heating to form two alkoxy radicals. In the second initiation step, a hydrogen atom is abstracted by the alkoxy radical...
Autoxidation of Ethers to Peroxides and Hydroperoxides
Ethers represent a class of chemical compounds that become more dangerous with prolonged storage because they tend to form explosive peroxides when standing in the air. Autoxidation is the spontaneous oxidation of a compound in air. In the presence of oxygen, ethers slowly oxidize to form hydroperoxides and dialkyl peroxides.
Hydroboration-Oxidation of Alkenes
In addition to the oxymercuration–demercuration method, which converts the alkenes to alcohols with Markovnikov orientation, a complementary hydroboration-oxidation method yields the anti-Markovnikov product. The hydroboration reaction, discovered in 1959 by H.C. Brown, involves the addition of a B–H bond of borane to an alkene giving an organoborane intermediate. The oxidation of this intermediate with basic hydrogen peroxide forms an alcohol.
Oxidative Cleavage of Alkenes: Ozonolysis
In ozonolysis, ozone is used to cleave a carbon–carbon double bond to form aldehydes and ketones, or carboxylic acids, depending on the work-up.
Ozone is a symmetrical bent molecule stabilized by a resonance structure.
Ozone is a symmetrical bent molecule stabilized by a resonance structure.
E2 Reaction: Kinetics and Mechanism
SN2 substitutions and E2 eliminations of alkyl halides proceed via a concerted pathway. While the nucleophile attacks the alpha carbon in SN2 reactions, it functions as a strong base and abstracts a beta hydrogen in the E2 mechanism. The rate-limiting transition state in E2 elimination reactions is characterized by partially broken carbon–hydrogen and carbon–halogen bonds and a partially formed pi bond between the alpha and beta carbons. The beta hydrogen and halide are eliminated...
Regioselectivity of Electrophilic Additions-Peroxide Effect
In the presence of organic peroxides, the addition of hydrogen bromide to an alkene yields the isomer that is not predicted by Markovnikov’s rule. For example, the addition of hydrogen bromide to 2-methylpropene in the presence of peroxides gives 1-bromo-2-methylpropane. This addition reaction proceeds via a free radical mechanism, which reverses the regioselectivity. The free radical reaction mechanism involves three stages: initiation, propagation, and termination.
