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organic sem 2 > 5b > Flashcards

5b Flashcards

1
Q

whats an imine

A

R R = NR

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2
Q

whats the pH of an imine

A

4-6

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3
Q

how do we form an imine

A

ketone + primary amine

acid catalyst: H+

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4
Q

describe imine formation from a ketone and a primary amine

A

O on C=O attacks H+
loe pair on amine attacks C
1-2 addition
base deprotonates the amine
OH is protonated
lone pair on amine helps remove water LG.
giving us an imine

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5
Q

what is an imminium ion

A

R R = N R R +

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6
Q

whats an organometallic

A

C - METAL

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7
Q

in organometallics,, what are the charges

A

C is slightly -
Metal is slightly +

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8
Q

organolithium

A

C-Li

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9
Q

organomagnesium

A

C-Mg X

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10
Q

in organo magnesium,, what can X be

A

Cl
Br
I

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11
Q

what do organometallics do

A

undergo nucleophilic addition reactions with ketones + aldehydes to give alcohols

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12
Q

what are organometallic reactions usually carried out in

A

THF
Et2O

aprotic solvents

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13
Q

bromobutane + Li in Et2O

A

alkyl lithium

the charges on the C and substituent switch!!

from C being +
to C being -

gives LiBr as a product aswell

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14
Q

bromobutane + Mg in Et2O

A

alkyl magnesium bromide

Grignard reagent

charges switch from C+ to C-

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15
Q

adding alkyl lithium to ketone // aldehyde

A

R-Li bond donates e- and attacks the C=O
= e- move to the O giving O-

O- then attacks H3O+ to give an alcohol.

either secondary or tertiary

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16
Q

reaction that forms alcohols from ketones or adehydes

A

1,2 addition

irreversible

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17
Q

making primary alcohols with MgXOH

A

H C=O H formaldehyde

the bond between MgX - R attack the C

then reacting with H3O gives an alcohol,, primary

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18
Q

what do we react carbonyls with to get alcohols

A

alkyl lithium

MgX - R

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19
Q

whats special condition needs to be present when making alcohols using R - MgX

A

in needs to be in anhydrous conditions as its sensitive to water

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20
Q

how do we synthesise a carboxylic acid

A

react R - MgX or R -Li with CO2

CO2 addition reactions

Co2 must be solid and in THF or Et2O

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21
Q

reaction for making carboxylic acids from CO2 and R-MgX

A

R-MgX bond attacks the C in CO2

attacks H3O+ to protonate the O- and give an alochol // carboxylic acid group

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22
Q

bromo butane to carboxylic acid!!

A

bromobutane + Mg in Et2O

gives butane - MgBr

add solid CO2 electrophile

gives butane CO2MgBr

add H3O+

gives butane - CO2H

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23
Q

addition of a metal hydrides to ketones or aldehydes

A

gives alcohols

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24
Q

metal hydrides

A

NaBH4
LiAlH4

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25
Q

what type of H do metal hydrides have

A

nucleophilic

the B-H or the Al-H bond attack smt positively charged

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26
Q

ketone + metal hydride

A

secondary alcohol

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27
Q

aldehyde + metal hydride

A

primary alcohol

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28
Q

bromonium ion

A

BH4 -

  • charge as B is in group 3
29
Q

BH3

A

6e- in the B-H sigma bonds

1 empty p orbital

30
Q

organolithium derivative

A

R - Li

31
Q

organolithium derivative charge

A

C = p-
Li = p+

32
Q

steps to think of mechanism for organometallics

A
  1. is the product a 1, 2, 3 alcohol
  2. reactant probably had one less carbon
  3. e- need to come from a C-Metal bond so add the Metal
33
Q

if product is a 1 alcohol the reactant must be

A

H H =O formaldehyde

34
Q

if the product is a 2 alcohol the reactant must be

A

aldehyde

35
Q

if the product is a tertiary alcohol the reactant must be

A

a ketone

36
Q

what are organometallics used for

A

they react with aldehydes and ketones,, aka carbonyls,, under 1,2 irreversible reactions to form alcohols.

37
Q

what must be used when an organometallic reacts with a carbonyl under 1,2 addition irreversible reactions

A

THF
Et2O
aprotic solvents

38
Q

what conditions must organometallic,, 1,2addition irreversible reactions be done in

A

anhydrous
organometallics are strong bases ,, aka they readily react with water/alcohols

39
Q

product of using organometallics

A

MgXOH
LiOH

40
Q

organometallics + CO2 electrophile gives

A

carboxylic acids

carboxylate salts

41
Q

halogenoalkane to carboxylic acid reaction

A

halogenoalkane + Mg + Et2O gives an organomagnesium derivative

add CO2 and H3O+

forms a carboxylic acid

42
Q

an addition reaction can also be a what reaction

A

reduction reaction

43
Q

why must NaBH4 be used instead of NaH

A

NaH is a strong base bc the H- have a large charge density

this is bc H is more electronegative than sodium

44
Q

where must the arrow start when drawing an addition // reduction reaction using BH4 or AlH4

A

from the X-H sigma bond

45
Q

what solvent must be used in reduction reactions // addition of metal hydrides

A

THF

46
Q

reduction reactions can also be called

A

addition reactions of metal hydrides

47
Q

borohydride anion

A

BH4 -

48
Q

borohydride anion to borohydride

A

react it with an electrophile to remove 1 of its Hs

leaves u with BH3 : 6e- in the sigma bonds,, 1 empty p orbital

and H-Electrophile is also a product

49
Q

ester with LiAlH4

A

primary alcohol
double reduction

50
Q

ester with DIBAL

A

aldehyde

51
Q

what must be done to DIBAL before it ca be a reducing agent

A

must form a lewis acid-base complex

52
Q

ester and NaBH4

A

cant reduce esters
lone pair on O,, pi donation via mesomeric effect which reduces the p+ on C,, making it less reactive

53
Q

1,2-addition of a hydride is what

A

a reduction reaction

54
Q

what does dibal look like

A

>

    • Al - - <
      doot doot claw ,, doot doot claw
      then a H bonded to the Al
55
Q

limitation of LiAlH4

A

cannot be used in protic solvents

56
Q

is NaBH4 the more powerful hydride donor aka reducing agent

A

no
LiAlH4 is the more powerful hydride donor aka reducing agent

57
Q

esters can be reduced to what using what

A

esters to aldehydes using DIBAL

esters to primary alcohols using LiAlH4 in Et2O (double reduction)

58
Q

mechanism of ester to aldehyde

A

use dibal
O: attacks the Al
H of dibal attacks C
lone pair on O removes O-R of ester
O-R of ester attacks Al

O is - Al is +

electrons from O-Al bond to Al
aldehyde is formed

59
Q

what is reductive amination

A

reducing imines to amines

60
Q

whats an imine again

A

R R = N R

61
Q

whats used to reduce imines to amines in reductive amination

A

Na(CN)BH3

62
Q

what is Na(CN)BH3

A

sodium cyanoborohydride
toned down version of borohydride,,
CN withdraws e-,, makes it a weaker reducing agent
mild hydride donor

63
Q

imine to amine synthesis

A

reduction called amination
uses Na(CN)BH3 as a mild reducing agent
done at pH6
selective to imines instead of aldehydes//ketones

64
Q

primary amine

A

N bonded to 1c and 2 h

65
Q

secondary amine

A

N bonded to 2 c and 1 h

66
Q

tertiary amine

A

N bonded to 3 c and o H
still has a lone pair tho.

67
Q

iminium ion description

A

imine: R R = N R
iminium ion: R R = N(+) R R

68
Q

natures most important oxidising agent

A

NAD+

69
Q

natures most important reducing agents

A

NADPH
NADH

organic sem 2 (14 decks)

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