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CH10136 > Nucleophilic Substitution- SN1 vs SN2 > Flashcards

Nucleophilic Substitution- SN1 vs SN2 Flashcards

1
Q

What are the three classifications of an organic solvent

A
  1. Polar protic
  2. Polar aprotic
  3. Non-polar
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2
Q

What is a polar protic solvent

A
  1. Capable for hydrogen bonding

2. O-H or N-H groups

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3
Q

Give 5 examples of polar protic solvents

A
  1. Water
  2. Acetic acid (AcOH)
  3. Methanol
  4. Ethanol
  5. Isopropanol (i-PrOH)
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4
Q

Give 6 examples of polar aprotic solvents

A
  1. Dimethyl sulfoxide (S+(Me)2O-) DMSO
  2. Dimethyl formamide (CHON(Me)2) DMF
  3. Acetonitrile (MeCN)
  4. Acetone (CO(Me)2)
  5. Tetrahydrofuran (4 carbon cyclic with O joining in middle) THF
  6. Ethyl acetate (EtOAc)
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5
Q

Give 3 examples of non-polar solvents

A
  1. Dichloromethane (CH2Cl2) DCM
  2. Diethyl ether (Et2O)
  3. Hexane (C6H14)
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6
Q

How can solvent polarity be quantified

A
  1. Using the dielectric constant E
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7
Q

How do polar protic solvents interact with anions and cations

A
  1. Cations stabilised by lone pairs

2. Anions stabilised by hydrogen bonding

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8
Q

How do polar aprotic solvents interact with anions and cations

A
  1. Cations stabilised by lone pairs

2. Anions not stabilised

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9
Q

What type of solvent do SN2 reactions work fastest in

A
  1. Polar aprotic
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10
Q

What type of solvent do SN1 reactions work fastest in

A
  1. Polar protic
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11
Q

How do SN1 and SN2 work in non-polar solvents

A
  1. No reaction occurs
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12
Q

Why do SN1 work faster in polar protic

A
  1. Transition states and intermediates are more polar than neutral starting materials
  2. Transition states are stabilised relative to the starting material
  3. So there is a lower activation energy and a faster rate of reaction
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13
Q

Why do SN2 reactions work faster in polar aprotic solvents

A
  1. SN2 using anionic nucleophiles have a transition state that is less polar than the starting materials
  2. Polar aprotic solvent cannot stabilise the anion but polar protic can
  3. Energy of starting materials increased relative to TS compared to Polar protic
  4. Lower activation energy and faster rate
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14
Q

Which reaction favours a tertiary substrate or one with a stabilised carbocation

A
  1. SN1
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15
Q

Which reaction favours methyl or primary alcohol

A
  1. SN2
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16
Q

Whihc reaction requires an excellent leaving group

A
  1. SN2
17
Q

Which reaction requires a good nucleophile

A
  1. SN2
18
Q

Which reaction only requires a good leaving group

A
  1. SN1
19
Q

Which reaction has its rate independent of the nucleophile

A
  1. SN1
20
Q

Which reaction prefers a polar protic solvent

A
  1. SN1
21
Q

Which reaction prefers a polar aprotic solvent

A
  1. SN2

CH10136 (30 decks)

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