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Zorluk: OrtaAlkenes and Alkynes: Preparation, Reactions, and Unsaturation Tests

What is the IUPAC name of the major organic product formed when one mole of hydrogen bromide (HBrHBr) reacts with prop-1-ene in the absence of peroxides?

Cevap: 2-bromopropane / 2-Bromopropane

Cevap

2-bromopropane
Electrophilic addition of hydrogen bromide to prop-1-ene without peroxides follows Markovnikov's rule. The hydrogen atom attaches to the terminal carbon (CH2CH_2), leading to the formation of a secondary carbocation intermediate. Subsequent nucleophilic attack by the bromide ion yields 2-bromopropane as the major product.

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1
Identify the reactants and the reaction type
The reaction takes place between an unsymmetrical alkene, prop-1-ene (CH3CH=CH2CH_3CH=CH_2), and hydrogen bromide (HBrHBr). This is an electrophilic addition reaction.
Alkenes readily undergo electrophilic addition across the unsaturated carbon-carbon double bond.
2
Apply Markovnikov's rule to determine carbocation stability
In the absence of peroxides, the reaction follows Markovnikov's rule. The proton (H+H^+) adds to the double-bonded carbon holding more hydrogen atoms (C1C1, CH2CH_2), generating a more stable secondary carbocation (CH3CH+CH3CH_3CH^+CH_3).
A secondary carbocation is more stable than a primary carbocation due to alkyl group electron-donating inductive effects.
3
Attach the bromide ion and name the resulting haloalkane
The bromide ion (Br−Br^-) attacks the secondary carbocation to form CH3CH(Br)CH3CH_3CH(Br)CH_3. The systematic IUPAC name for this compound is 2-bromopropane.
Numbering the three-carbon parent chain gives the bromine substituent locant position 2.

Anahtar Kavram

Markovnikov's rule in electrophilic addition reactions of alkenes
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Konular

Alkenes and Alkynes: Preparation, Reactions, and Unsaturation Tests

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