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Chemistry > Acids, Bases, Esters, Aldehydes and Ketones > Flashcards

Acids, Bases, Esters, Aldehydes and Ketones Flashcards

1
Q

Carboxyl functional group

A

COOH

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2
Q

Nomenclature of carboxylic acids

A

Alkane + oic acid

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3
Q

Why are carboxylic acids weak

A
  • There is low dissociation of H+ ions
  • There is a higher concentration of carboxylic acid than H+
  • The equilibrium lies towards the carboxylic acid
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4
Q

What is an oxonium ion

A

When an acid is added to water it donates a proton to a water molecule which forms a dative covalent bond

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5
Q

How does a base act in water

A

It accepts one of waters protons causing the formation of a hydroxide ion (OH-)

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6
Q

What is dissociation

A

The breaking of the bond between a hydrogen atom and a electronegative atom by heterolytic fission to leave a proton and a negative ion

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7
Q

What is a conjugate base

A

The anion formed after an acid dissociates e.g. Cl- from HCl

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8
Q

What makes an acid strong or weak

A

An acid gets stronger the higher the percentage of their atoms dissociate, this is not affected by concentration

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9
Q

What is the acid dissociation constant formula

A

Ka =[H+][A-]/[HA]

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10
Q

What is pKa and its formula

A
  • Its the constant for weak acids
  • pKa = -log10 Ka
  • The bigger the Pka the weaker the acid
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11
Q

Why do different molecules have different amounts of dissociation

A
  • The stronger the O-H bond the weaker the acid as its harder to donate a proton
  • Sulfuric acid has lots of electronegative oxygen atoms which withdraws electrons away from th O-H so it is easier to break
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12
Q

What is the formula for pH

A

pH = -log10 [H+]

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13
Q

What is the trend in boiling points for carboxylic acids

A

As the length increases so does the boiling point due to more induced dipole-induced dipole attractions

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14
Q

What is a titration curve

A

Its the plotting of the change in pH of a titration. The pH is plotted against the volume of alkali added

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15
Q

What is the equivilance point

A

The middle of where there is a large change in pH but small addition of alkali it can also be called the neutralisation point

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16
Q

What do the 4 different titration curves look like

A
  1. A strong base and a weak acid will have a small vertical portion from about 3 to 8 which is high up
  2. A weak base and weak acid will have a very shallow change so indicator will be hard to determine
  3. A weak base and a strong acid will have a medium vertical portion from around 4 to 11
  4. A strong base and strong acid will have a long vertical portion from around 2 to 10
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17
Q

What are the indicators and their ranges

A

Litmus = 5-8
Methyl orange = 3.1-4.4
phenolphthalein = 8.3-10

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18
Q

How to get carboxylic acids from esters

A

The ester is refluxed with a dilute acid or alkali

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19
Q

How to get carboxylic acids from amides

A

Reflux them with a dilue acid or alkali

20
Q

What is esterification

A

The production of an ester by refluxing a carboxylic acid with an alcohol in the presence of an acid, an equilibrium mixture is produced

21
Q

What are acyl chlorides

A

Carboxylic acids with their OH group replaced by a Cl

22
Q

Nomenclature of acyl chlorides

A

The oic acid is replaced by an oyl chloride

23
Q

Why are acyl chlorides useful

A

The carbon is very susceptable to nucleophilic attack due to the highly elecronegative chlorine atom

24
Q

How are acyl chlorides produced

A

Carboxylic acids react with sulfuryl chloride or phosphorus chloride

25
Q

Nomenclature of esters

A

They are split into a carboxylic acid section and an alcohol section, yl and oate e.g. methyl ethanoate

26
Q

Formula for the equilibrium constant

A

Kc =[C]^y[D]^z
——-
[A]^w[B]^x

		 Where wA + xB = yC + zD
27
Q

What does a high equilibrium constant mean

A

That at equilibrium the concentration of products is alot higher than the reactants

28
Q

How are esters hydrolysed

A
  • Water reacts with the carbonyl carbon eliminating the alcohol
  • This can be made quicker with a base, boiling an ester with soduim hyroxide forms the salt of the acid and the alcohol
29
Q

What mechanism do acyl chlorides undergo

A

An addition-elimination reaction

  1. A nucleophile e.g. water attacks the carbonyl carbon
  2. The C=O bond is broken and the electrons are transfered to the oxygen
  3. The hydrogens are rearranged
  4. The electrons from the O-H bond are transfered to the C=O reforming the double bond
  5. The chlorine is lost
  6. HCl is formed as a product
30
Q

Nomenclature for amides

A
  • Carbonyl with NH2 attached
  • The suffix amide to the chain e.g. ethanamide
31
Q

Reaction of ammonia with acyl chlorides

A
  1. Ammonia attacks the carbonyl carbon
  2. Double bond is broken and oxygen become negative
  3. Hydrogen transfered to the O-
  4. O-H bond electrons transfered to form a C=O and Cl bond broken
32
Q

Nomenclature of nitriles

A

A chemical with CN will be called its alkane and end in nitrile e.g. ethanenitrile

33
Q

Preperation of amides

A
  • Reaction cyanide ions with halogenalkanes
  • Reacting HCN with aldehydes or ketones
34
Q

Hydrolysis of nitriles

A
  • Very slow in water
  • Faster in acidic or basic conditions
  • When done in acid a carboxylic acid and ammonium salt is produced
  • When done in a base a carboxylate and ammonia is formed
35
Q

Reduction of nitriles

A

an be reduced using a strong reducing agent to form a primary amine

36
Q

How to work out [H⁺]

A

[H⁺] = log^pH

37
Q

What does the carbonyl functional group contain

A

C=O

38
Q

Whats the difference between Aldehydes and Ketones

A
  • Aldehydes contain the carbonyl at the beginning or end
  • Ketones have the carbonyl group in the middle
39
Q

How are aldehydes and ketones formed

A

Aldehyde - Oxidisation of a primary alcohol

Ketone - Oxidisation of a secondary alcohol

Potassium dichromates with sulphuric acid is the oxidising agent

40
Q

Formation of carboxylic acids

A

Heating primary alcohols under reflux

41
Q

Tollens test

A
  • Tollens reagent has [Ag(NH3)2]- ions
  • Add ammonium
  • When warmed with the reagent an aldehyde will be oxidised
  • The silver will solidify and become reflective
  • A ketone wont be oxidised so the silver wont solidify
42
Q

Fehlings test

A
  • Copper(II) ions act as an oxidising agent
  • If an aldehyde is warmed with it the Cu(II) ions get reduced to Cu+ ions
  • The colour changes from blue to red if a aldehyde is present
  • The colour change is not observed with a ketone
43
Q

Oxidisation of primary and secondary alcohols

A
  • Done by potassium dichromate
  • An orange to green colour change is observed
  • Primary -> Aldehyde
  • Secondary -> Ketone
44
Q

Addition of HCN to carbonyls to form nitriles

A
  • The cyanide attacks the carbon
  • The electrons from the Pi bond are transfered to the oxygen making it negatively charged
  • The negative oxygen bonds to the H+
45
Q

The general mechanism with both aldehydes and ketones

A
  • A nucleophile attacks the carbon
  • The Pi bond is broken giving its electrons to the oxygen making it negatively charged
  • The oxygen attracts a H+

Chemistry (4 decks)

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