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A2 CHEMISTRY > Organic chemistry topic 17 ( aldehydes, ketones , carboxylic acids , esters,Acyl chlorides > Flashcards

Organic chemistry topic 17 ( aldehydes, ketones , carboxylic acids , esters,Acyl chlorides Flashcards

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1
Q

I want an aldehyde ? How do I make it ?

2

A
  • distill and heat primary alcohol
  • partial oxidation with potassium dichromate
  • orange to greeen
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2
Q

How do I make a carboxylic acid?
?
2

A
  • Reflux with potassium dichromate
  • Primary ALCOHOL
  • heat
  • orange to green
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3
Q

Name all tests for aldehyde and ketone ?

4

A

1 ) fehlings and bens

2) Tollens
3) potassium dichromate
4) Brady’s

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4
Q 
Positive test for Brady’s test ? 
What does it test for ? 
Condition?
PPt? 
4
A
  • tests for carbonyl group = ketones and aldehydes
  • dissolved in methanol , concentrated h2so4
  • if it’s positive and aldehyde and ketone is present then = BRIGHT ORANGE PPt
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5
Q

What mechanism does the cyanide + aldehyde or ketone ? 1

A
  • nucleophilic ADDITION
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6
Q

What reagents can we use for the cyanide reaction ?

2

A
  • HCN

- KCN in cold alkaline solution

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7
Q

Positive test in fehlings and bens solution colour ?

1

A
  • Blue to brick red
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8
Q

Outline tollens test ?
3
2 reagents and ppt?

A
  • add silver nitrate and nh4cl should form a:
    SILVER MIRROR PPT
    When aldehyde is present
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9
Q

How do you form an Ester ?

3

A
  • CONC ACID CATALYST ( HCL or h2so4)
  • DISTILL CARB ACID + ALCOHOL

To obtain pure product you should:
Add na2co3 to remove any carb acid left( because it’s a reversible reaction )

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10
Q

How do we get a carb acid or alcohol from an ester?
4
What’s it called?

A
  • REFLUX
  • dilute hcl or h2so4
  • acid hydrolysis
  • reversible
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11
Q

How do we carry out base hydrolysis on an Ester ?

4

A
  • REFLUX
  • with weak base NAOH
  • you get the carboxylate ion and an alcohol
  • IRREVERSIBLE
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12
Q

How do we carry out triodomethane reaction ?
What does it test for ?
3

A
  • tests for : methyl carbonyl group next to carbon
  • add NAOH and I2 ∧heat
  • yellow ppt should form for positive result
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13
Q

Why is the triodomethane reaction useful?

1

A
  • shortens the carbon change by one
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14
Q

What mechanism is the liAlH4 reducing reaction ?

A
  • nucleophilic addition
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15
Q

What is the liAlH4 ?

What does it do ?

A
  • reducing agent

- converts the aldehyde and ketone back to the ALCOHOL !

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16
Q

How do I make ketone ?

3

A

A reflux secondary alcohol
Potassium dichromate
Orange to green

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17
Q

How can I oxidise a tertiary alcohol ?

1

A

Burn it

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18
Q

Solubility of carboxylic acids ( as the carbon chain increases) …
1

A
  • the solubility decreases
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19
Q

Hydrolysis (acid) of Nitriles forms ?
- conditions ?
2

A
  • Carboxylic acid + NH4CL

- reflux with dilute HCL

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20
Q

Carboxylic acid + NAOH —>
With carbonates ?
2

A
  • salt and water
    Sodium ethanoate
    With carbonates forms :salt, water and CO2
21
Q

How can we reduce Carboxylic acid ? What do we use ?
( why in dry ether )
4

A
  • liAlH4 in DRY ETHER( so no H+ is present otherwise; H- + H+ —> H2 ( BANG) )
  • you can reduce the Carboxylic acid to a primary alcohol!
22
Q

Functional group of Ester ?

1

A

-COO-

23
Q 
Ester are made by ?
Used for ? 
Conditions and reaction ? 
4
two ways if making an ester
A
  • Carboxylic acid and alcohol (or acyl chloride and alcohol,non reversible reaction and produces hcl too )
  • reversible reaction
  • REFLUX & CONC sulfuric acid catalyst
  • forms Ester and water !
  • used for flavourings ( and scents )
  • pear , banana , pineapple ( etc )
24
Q

In the hydrolysis of an Ester why do we use DILUTE h2so4?

3

A
  • it’s an equilibrium reaction
    -Carboxylic acid+alcoholEster + water
    If the catalyst is dilute the water concentration rises and the equilibrium shifts to the LHS forming the acid and water !
25
Q

How is base hydrolysis of an Ester more efficient than acid hydrolysis ?
3
How do you obtain a carboxylic acid ?

A
  • it’s not reversible
  • used dilute NAOH
  • you get Carboxylate ion and alcohol
  • you have to react it with dilute HCL to obtain a carboxylic acid
26
Q

How are polyesters formed ?

1

A
  • condensation reaction
27
Q

What are the requirements to form a polyester ?
What is removed from each ?
4

A
  • Dicarboxylic acid
    -Diols
    ( so 2 groups on each )
    Note:
    -from carboxylic acid —> OH IS ALL REMOVED
    -from Diol —> ONLY H IS REMOVED
28
Q

What’s the functional group for acyl chlorides ?
Formula ?
What makes them reactive ?
3

A

-COCL-
Formula : C(n) H(2n-1)OCl
-they easily lose their Cl

29
Q

Acyl chloride + water —>?

1

A
  • carboxylic acid and HCL
30
Q

Acyl chlorides + alcohols =>

1

A

ESTER + HCl

31
Q

Acyl chlorides + NH3=>?

1

A

AMIDE + HCL

32
Q

Acyl chlorides + AMINES =>?

1

A

N substituted AMIDE + HCl

33
Q

What happens in Sn1?
What kind of isomer does it form ?
What kind of products take sn1?
3

A

1- group breaks off leaving planar intermediate
2-nucleophile attacks ( it can attack from either side of the intermediate )
3-this gives rise to 2 optical isomers
SN1 is usually taken by tertiary halogenoalkanes

34
Q

What happens in SN2?
What molecule takes SN2?
Isomers ?
4

A

1- one step reaction
2-nucleophille always attack opposite side to the leaving group of the TRANSITION STATE
3-only one OPTICALLY ACTIVE SINGLE ENANTIOMER
This rotates the plane polarised light differently to the reactant

35
Q

What’s an ENANTIOMER?

2

A

-optical isomers produced by chiral carbon

36
Q

What’s a Racemic mixture ?

2

A

A mixture which contains equal quantities of each ENANTIOMER of a chiral compound

37
Q

Aldehydes and ketone have low boiling points becauseeeee ….
1

A

No hydrogen bonding within themselves

38
Q

Why are short aldehydes and ketones soluble in water ?

1

A

They form Hydrogen bonds with water

39
Q

Why are long chain aldehydes and ketones not soluble In water ?
3

A
  • long carbon chain = hydrophobic is it disturbs hydrogen bonds within the water molecule
  • if the hydrocarbon chain is long enough then the VDW’s forces will be great and so will the hydrogen bonding
40
Q

whats the strongest intermolecular bond in an aldehyde or ketone-why ? 2

A

-C=O is a polar bond .
-This means it can form Permanent DIPOLE -DIPOLE
forces

41
Q

why are long chain aldehydes less soluble in water ?

4

A
  • in aldehyde solubility is due to the hydrogen bonding between the C=O and the balance between the hydrophobic carbon chain
  • in longer aldehydes , the Hydrophobic region is bigger meaning that they aren’t soluble in water.
42
Q

Reducing with LiAlH4 in aldehydes or ketones is the same as … 1

A
  • adding H2 to the double bond .
43
Q

What does Tollen’s reagent do to an aldehyde? 1

A

oxidise it to a Carboxylic acid

44
Q

whats a positive test in the iodoform test - triiodomethane reaction ?

A

yellow ppt of CHI3 always produced .

checks for —ch3—c=o group

45
Q

Why does sodium ethanoate have a higher melting point than Ethanoic acid ? 2

A
  • sodium ethanoate has ionic bonding and this is harder to over come than the hydrogen bonds between Ethanoic acid molecules .
46
Q

hydrolysis of a nitrile with aq hcl = ?

2

A

1)R—-COOH + NH4Cl

so ammonium chloride + carb acid

47
Q

hydrolysis + heat a nitrile with dilute NaOH

2

A

R—CO2- Na+ + NH3

carboxylate ion + ammonia

48
Q

why do we need dilute acid to hydrolyse an ester yet a concentrated acid to make an ester ?
3

A

we need dilute HCl hydrolyse ester as it is reversible reaction.
ester+ water acid+alcohol
so if water is in excess than equilibrium shift to the RHS so hydrolysis happens quicker !
hence why dilute ( higher concentration of water molecules ) acid catalyst is used .

A2 CHEMISTRY (8 decks)

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