Electrophilic Addition in Alkenes Flashcards

1
Q

How many steps is electrophilic addition and what is the reaction similar to?

A

2 steps and reverse of an E1 reaction

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2
Q

What is the hybridization of the carbons involved in the double bond in the carbocation?

A

One that accepted hydrogen: sp3
One with positive charge: sp2

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3
Q

In electrophilic addition, what is always the electrophile source?

A

H+ from an acid

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4
Q

What is the difference between using concentrated sulfuric acid and diluted?

A

Concentrated created alkyl-hydorgensulphate however in diluted the water replaces the bisulphate ion (as water is a better nucleophile) and turns the molecule into an alcohol instead

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5
Q

Why is water a better nucleophile than the sulfate ion

A

sulfate ion is a weak base as it comes from a strong acid thus does not + the sulfate ion is very stable thus does not really need to react

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6
Q

What are the 2 steps in electrophilic addition?

A
  1. Protonation and formation of carbocation
  2. Nucleophile attacks positive carbon center to generate new single bond
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7
Q

What determines where the hydrogen is attacked in asymmetrical alkenes?

A
  • positive charge should be on the more substituted carbon due to hyperconjugation
  • resonance may help stabilize carbocation
  • hydrogen should go to the carbon with the most hydrogens already
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8
Q

what are the 2 types of selectivity and what are their differences

A

regioselective: one product is formed in a greater amount than another (major minor)
regiospecific: only one possible product is formed

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9
Q

Is reaction under kinetic control? What does that mean?

A

It is under kinetic control because the major product is caused by the rate of reaction rather than the stability of the product

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10
Q

Is a carbon radical or carbocation more stable and why?

A

The carbocation is more stable because in creation of the 2 new MOs as a result of hyperconjugation carbocations have 2 electrons in the lower MO while radicals have an additional electron in the higher MO which destabilizes the molecule

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11
Q

Why does the nucleophile not attack the positive charge when it can be delocalized into the ring?

A

Loss of aromaticity if attack on the ring, HIGHLY UNFAVOURABLE (not thermodynamically liked)

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12
Q

Why can electrophilic addition and radical addition result in different products?

A

In each reaction a different species attacks first, for EA it is the positive hydrogen and in radical it is the radical substituent (still based on radical stability)

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13
Q

What is the stereochemistry of the electrophilic addition reactions?

A

Enantiomers (R and S) as the nucleophile has equal probability of attack from both sides of the planar molecule

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14
Q
A
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