substitution Flashcards

1
Q

how does substitution occur?
1. SN1
2. SN2
Are they exomthermic or endothermic

A

it is the reaction between l.g. and nu-
1. lg leaves first then nu- attacks
2. lg ‘s leaving and nu- add takes place simultaneously

Exothermic

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2
Q

Rate of SN1 is directly dependent on?

A
  1. R-X conc
  2. C+ stabilty before rearrangement
  3. X- stability
  4. presence of EWG(stronger the ewg quicker and easier will be the rds step)

since it is the rds step in SN1 .i.e. R-X–> R+ + X-

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3
Q

how does nature of substrate effect rate of SN1

A

substituted benzylic>3RX>benzylic>allylic
R-X -3 º > 2 º > 1 º

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4
Q

nature of leaving group effect in SN1
(same for SN2)

A

better lg=>more rate
R-I > R-Br > R-Cl > R-F

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5
Q

nature of solvent where Sn1 if favoured

A

pps

it solvates both R+ AND X-

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6
Q

nature of solvent where Sn2 if favoured

A

paps

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7
Q

attack in SN1 takes place from which side

A

practically, IOC
theoretically, IOC%=ROC%

ROC= FRONT(not rear) IOC=BACK(inversion)

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8
Q

basic difference b/w SN1 and SN2

A

SN1- C+ stability, becuz R+ rds mein banta hai
SN2- less steric hinderance becuz one step process, nu- tabhi lagega agr crowding na ho rahi ho

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9
Q

SN2 roc or ioc

A

Always IOC(back side), to avoid steric hinderance

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10
Q

Rate of SN2 depends upon

A
  • Stability of T.S.
  • EWG
  • Nu- Concn.
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11
Q

Nature of substrate in R-X in SN2

A

R-X: 1 º > 2 º > 3 º

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12
Q

Rate of SN2 @hinderance

A

unhindered> α hindered> βhindered

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13
Q

R-X + NaI(acetone) gives

A

R-I +NaX

Finklestein reaction SN2

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14
Q

R-X + [AgF, HgF2, SbF5]MF- gives

A

R-F + MX

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15
Q

ETHER* [R1-O-R2 ]* + H2O/H+(acidic hydrolysis)

A

R1-OH + R2-OH

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16
Q

R1-O-R2 + HI gives

A

R1/R2I +R1/R2-OH
depending upon less steric hinderance in anhydrous
aqueous mein oh oh lege ga