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Chemistry > Grasby > Flashcards

Grasby Flashcards

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1
Q

What do you get when you react R-X (X is a halide) with NaCN

A

Nitrile

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2
Q

How can carboxylic acids be made from CO2

A

By reacting it with an organometallic reagent which breaks one of the C=O. this is then followed by an acid work up

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3
Q

What does a high pKa indicate

A

Strong acid

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4
Q

What does a low pKa mean

A

Strong base

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5
Q

Arrange these in terms of which is the best LG and state their pKa`s,

Amine, anhydride, acid chloride and alcohol

A

Chloride (HCl = -7)
Anhydride (RCOOH = 5)
Alcohol (ROH = 15)
Amine (RNH2 = 35)

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6
Q

If XH has a low pKa it shows that it is a…

A

good leaving group

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7
Q

How can esters be made from acid chlorides and anhydrides

A

React ROH with base

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8
Q

What role does the base play in ester formation from acid chlorides and anhydrides.

A

Takes a H from the alcohol group once it has attacked the carbonyl

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9
Q

What do you get when you react an acid chloride with a carboxylate salt eg MeCOO-

A

Anhydride

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10
Q

What do you get if you react an acid chloride with 2 equalivalents of an amine

A

Amide

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11
Q

Why are two equivalents of amines needed in the reaction with acid chlorides

A

One to form the amide and the other to mop up the acidic H

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12
Q

Esters and anhydrides can also be used to form amides but why is chloride preferred

A

Bigger yield

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13
Q

describe the schotten bauman conditions for the reaction of amides and why does this not produce a carboxylic acid.

A

2 equivalents of amine. NaOH and CH2Cl2.
This reaction takes place in the organic phase.

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14
Q

What makes a good nucleophile

A

Strong bases and molecules with high pKa`s

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15
Q

Order these in terms of decreasing electrophilicity
Ester, amine, chloride and anhydride

A

Chloride - anhyrdried- Ester - amine

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16
Q

How does the inductive effect increase electrophilicity

A

More inductive effects increases the electrophilicity

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17
Q

How does delocalisation affect electrophilicity

A

Decreases electrophilicity,however, lp in oxygen are lower in energy than lp in amides due to O being higher in electronegativity which means N donated lp

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18
Q

Why do anhyrdrides have high electrophilicity

A

Delocalisation is shared over two carbonyls

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19
Q

Can amides be made from carboxylic acid

A

No only from acid deratives

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20
Q

How are acid chlorides made from carboxylic acid

A

By reacting CA with SOCl2 or PCl5

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21
Q

How can electrophilicity be enhanced

A

protonate the carbonyl

22
Q

how can leaving group ability be enhanced

A

By protonating the Lg

23
Q

What conditions are needed for esterification

A

CA and an alcohol in acidic conditions

24
Q

Why is acid needed in esterification

A

To protonate the carbonyl and OH and also the reaction does not occur at a practical rate without acid catalysis.

25
Q

How to favour hydrolysis

A

XS water

26
Q

To favour Esterification

A

Use XS solvent eg ROH and remove H2O by using a drying agent or by distillation

27
Q

how are Lactones formed (Cyclic esters)

A

undergo intramolecular esterification.

functional groups more likely to interact if attached to same molecule

28
Q

Why cant esters be made under basic conditions

A

a carboxylate salt is formed

29
Q

What is transesterification

A

Conversion of one ester to another

30
Q

Does transesterication involve protonation of electrophile and leaving group

A

yes

31
Q

What do you get if you react esters with water under basic conditions.

A

Carboxylate salt and alcohol

32
Q

In saponification once the OH has be deprotonated is the reaction reversible

A

No as the carboxylate salt is not a nucleophile

33
Q

Why is an acid catalyst not needed when there is a good nucleophile

A

The nucleophile will be protonated turining it to a good one to a poor nucleophile.

34
Q

Explain the effect increasing acid has on imine formation

A

increases untill pH 5 then decreases

35
Q

How does an acid catalyst speed up the rate of imine formation

A

Converts poor lg into a good lg unitl pH 5

36
Q

What do you get if you react an amide with water under acidic conditions

A

carboxylic acid

37
Q

What do you get when an amide reacts with water under basic conditions

A

Carboxylic salt

38
Q

What is required to hydrolyse nitriles

A

Water and H2SO4

39
Q

What do you get when ROCL and an anhydride react with water

A

Carboxylic acid

40
Q

Why can`t esters be made from ketones

A

Because the product is more reactive and will react with the reagent.

41
Q

How are organocopper reagents made

A

CuBr is reacted with R-Li and ether at 78 degrees. which gives R2Cu-Li- and LiBr

42
Q

What do you get when you react an amide with a R-Li (ether and H3O+)

A

aldehyde

43
Q

What do you get when you react a nitrile with a grignard reagent followed by an acid workup

A

Ketone

44
Q

What is reduced by NaBH4

A

Ketones and aldehydes

45
Q

What is reduced by LiALH4 and acid workup

A

esters, anhydrides and chloride, even aldehydes and ketons

46
Q

What do you get when you react amide and LiAlH4

A

amine

47
Q

How do you get an aldehyde from an ester

A

reduce the ester with LiAlH4 followed by an acid work up and then react the alcohol with PCC, CH2Cl with no water.

48
Q

Name some properties of amino acids

A

All chiral except glycine and have the same stereochemistry. At pH 7 as zwitterions

49
Q

what do you get if you react an acid chloride and carboxylate salt

A

anhydride

50
Q

What do you get if you react an ester with an amine and comment on the rate of reaction

A

Amide and reaction is slow

51
Q
A

Chemistry (22 decks)

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