Unit 4.5 Carboxylic Acids Flashcards
What is the pH of ethanoic acid?
3 pH
What is the pH of phenol?
5 - 6 pH
What is the pH of water?
It should be 7 pH
What is the pH of ethanol?
7.3 pH
How is an ethanoate ion created?
Ethanoic acid + water
Equation formula of the creation of ethanoate ion
CH3COOH + H2O ⇌ CH3COO- + H+/H3O+
How do acids tend to dissociate
(2-way)
- When in water
- liberating a hydrogen ion
How do u determine the strength of an acid?
(1 + additional thing)
- How well they dissociate in H2O
- The more H+(aq) ions dissociated = strong acid
Explain stabilisation of ethanoate ion?
(3-way)
- More stable than phenoxide ion
- as negative charge can be delocalised
- over the 2 equivalent oxygen atoms
Equation of ethanoate ion stabilisation?
(might be asked to draw, so get whiteboard)
H3C(=O)O- <-> H3CO-(=O) -> H3CO–O (- in between o’s)
Highly refer to booklet
Explain stabilisation of phenoxide ion?
(2-way + 2-way)
- Stabilised through resonance of the negative charge
- through the ring system
- Less stable than ethanoate
- as the resonance structures aren’t equivalent
Explain stabilisation of ethanol?
(2-way + 2-way)
- Very little tendency for ethanol,
- to give away the proton
- No resonance structures possible
- to support the negative charge
Ethanoic acid rxn with sodium hydroxide?
(2 things)
- Reacts
- Acid neutralised to form a salt
Ethanoic acid rxn with metal carbonate?
(2 things)
- Reacts
- Formation of CO2 gas (effervescing)
Phenol rxn with sodium hydroxide?
(2 things)
- Reacts
- Acid neutralised to form a salt
Phenol rxn with metal carbonate?
No reaction.
Ethanol rxn with sodium hydroxide?
No reaction.
Ethanol rxn with metal carbonate?
No reaction.
What is the equation for the formation of a carboxylic acid from a primary alcohol?
([O]-> means oxidation)
H3CCH2OH [O]-> H3CCOH [O]-> H3CCOOH
What’s an oxidant that can oxidise primary alcohols to a carboxylic acid?
Acidified potassium dichromate (VI)
Chemical formula for acidified potassium dichromate?
H+/K2Cr2O7
What is the colour change observation of the formation of a carboxylic acid from a primary alcohol?
Orange to green
But what are primary alcohols usually form into after being oxidised?
(2 things)
- Aldehydes
- Carboxylic acids
And what do secondary alcohols form after being oxidised?
Ketones
What conditions needed for the oxidation of primary/secondary alcohols?
[Heat] under reflux
What about tertiary alcohols formation after being oxidised?
(4 !!! things)
- Resistant to oxidation
- Under severe conditions however
- May yield carboxylic acids
- Containing fewer carbon atoms than parent alcohol
How may the oxidation of the primary alcohol be sometimes considered a two-stage process?
(1 thing + 3-way)
- To obtain the aldehyde…
- Mild conditions must be used with the aldehyde
- distilled off as it forms
- to avoid carboxylic acid formation
Draw the eqn of the 2-stage process version of oxidation of a primary alcohol
(Prob refer to booklet, whiteboard)
H3CC(OH)H2 -> H3CH(=O) -> H3C(=O)OH
First -> = [O] & distillation
Second -> = [O]
A secret arrow from beginning to end = [O] & reflux
How are carboxylic acids reduced?
With the use of Lithium Aluminium Hydride
(LiAlH4)
What conditions are required to reduce carboxylic acids?
In ethoxyethane (diethylether) ^｡^
Write the eqn of the reduction of propanoic acid, state conditions required too
(Whiteboard)
CH3CH2COOH + 4[H] -> CH3CH2CH2OH
-> = (LiAlH4) in ethoxyethane
How would u form aromatic carboxylic acids?
Oxidation of an aromatic ring next to the alkyl group
What’s the oxidising agent used for the formation of aromatic carboxylic acids?
and then what?
- Alkaline potassium permanganate
- Acidifcation (HCl aq)
How is formation of aromatic carboxylic acids allowed?
(2-way + 2-way)
- Alkyl group influenced by
- neighboring aromatic ring
- Somewhat like special reactivity of
- alpha C-H bonds
Draw the eqn of oxidation of 4-bromomethylbenzene indicating conditions required ig?
(Whiteboard)
“4-bromomethylbenzene” -> [the aromatic carboxylic acid]
-> = 1, KMnO4/OH-
2, (H2O) HCl (aq)
Define decarboxylation?
Getting rid of a carboxylic acid
How do u perform decarboxylation?
(True 4-way)
- If carboxylic acid/its sodium salt
- strongly heated with sodalime
- carbon atom removed
- producing an alkane & a carbonate
Eqn of a typical decarboxylation of a carboxylic acid
(Whiteboard)
CH3CH2COOH + 2NaOH -> CH3CH3 + Na2CO3 (+H2O)
What are the usual decarboxylating reagents?
(2)
- NaOH
- or (preferably) sodalime
Why is decarboxylation often carried out using the sodium salt of the acid…. RATHER than the acid?
Generally more effective
Eqn of the sodium salt version
(Decarboxylation)
(Whiteboard)
CH3CH2COONa + NaOH -> CH3CH3 + Na2CO3
What is decarboxylation an example of?
- Descending homologous series
- in which means the length of
- carbon chain decreases
What’s next?
- Formation of nitriles
- Hydrolysis of Nitriles and Amides
- Reduction of nitriles
(Apparently some of these have 4.4 stuff too…. just great right ¬.¬)
The issue is that it’s not rlly the best clarification. Or maybe because i’m too comfortable at my environment. Or maybe the timing was definitely impeccable
Typical general formula of esters?
RCOOR1
And well, It’s like the carbon within connected to both =O and -O
It should be easy to understand…. assuming ik how to draw it D:
How do u prepare esters from a carboxylic acid?
(3 things)
- Heat w/
- Carboxylic acid + alcohol
- In presence of an acid catalyst
Eqn of the preparation of esters thru ethanol + ethanoic acid
(whiteboard)
C2H5OH + CH3COOH -> CH3COOC2H5 + H2O
-> = H+ & 60°C
What’s the function of the acid catalyst for the preparation of esters from the conversion of carboxylic acids?
(1 thing + 2-way)
- Protonate the carboxylic acid
- To allow resulting positive species
- to undergo nucleophilic attack by the alcohol
The end process for the preparation of esters from the conversion of carboxylic acids?
(3-way)
- Elimination of a proton
- and a molecule of water
- results formation of the ester
What’s a convenient route for the creation of esters from the conversion of carboxylic acids?
(3 points)
- Use dry (gaseous) hydrogen chloride as catalyst
- Results better yields (no alkene side chain formed)
- The Fischer-Speier method
How would u form internal esters?
(1 thing + 2-way)
- Only in some hydroxyacids
- Their ring structure of such an ester…
- broken on hydrolysis
How would u perform ester hydrolysis?
(4-way)
- Heat w/
- dilute mineral acids
- (hydrochloric/sulfuric acid)
- Ester = hydrolysed
What are the 2 hydrolysis’ that can be performed on the ester?
- Acid hydrolysis
- Alkaline hydrolysis
Show the eqn of acid hydrolysis on the ester
(Whiteboard)
RCOOR1 + H+/H2O -> RCOOH + R1OH
Show the eqn of alkaline hydrolysis on the ester
(Whiteboard)
RCOOR1 + NaOH -> RCOONa + R1OH
How would u gain the sodium salt from alkaline hydrolysis on the ester?
Add a dilute acid
(HCl)
How would u form acid chlorides from the conversion of carboxylic acids?
(2-1way)
- Reaction between carboxylic acid
- and phosphorus pentachloride (PCl5)
- Yields acid/acyl chlorides
Eqn of formation of acid chlorides from the conversion of carboxylic acids?
(Whiteboard)
CH3COOH + PCl5 -> CH3COCl + POCl3 + HCl
CH3COCl = ethanoyl chloride
POCl3 = phosphoryl chloride
Alternate reagents for the formation of acid chlorides from the conversion of carboxylic acids?
(Only 2)
- Phosphorus trichloride
- Sulphur dichloride oxide (thionyl chloride)
Eqn of formation of acid chlorides with phosphorus trichloride?
(Conversions of carboxylic acids)
(Whiteboard)
3 CH3COOH + PCl3 -> 3 CH3COCl + H3PO3
Eqn of formation of acid chlorides with sulphur dichloride oxide (thionyl chloride)?
(Conversions of carboxylic acids)
(Whiteboard)
CH3COOH + SOCl2 -> CH3COCl + SO2 + HCl
What does it mean if acid chlorides are reactive and acylating agents?
(2-way)
- Reagents which can introduce…
- the RCO- group into a molecule
Which is more reactive?
CH3COCl (Ethanoyl chloride)
or
C6H5COCl (Benzoyl chloride OR benzenecarbonyl chloride)
….. It’s ethanoyl chloride.
The CH3COCl
How would u gain the carboxylic acid back from an ethanoyl chloride?
(2 things)
- Acid chloride hydrolysis
- Ethanoyl chloride readily hydrolysed by water
Eqn of the hydrolysis of ethanoyl chloride?
(Whiteboard)
CH3COCl + H2O -> CH3COOH + HCl
What happens when u open a bottle of ethanoyl chloride?
(3-way)
- Misty fumes of hydrogen chloride seen
- as compounds reacts with….
- atmospheric water vapour
Rate of hydrolysis between acid chloride and ester?
Acid chloride > Ester
What is an amide?
a -C(=O)NH2 group
How would u form amides from carboyxlic acids?
(1-2way)
- Dehydration of the ammonium salt of the acid
- Excess of the acid is refluxed
- … w/ ammonium carbonate for several hrs
Eqn of the formation of amides
(Conversion of carboxylic acids)
(Whiteboard)
2 CH3COOH + (NH4)2CO3 ⇌ 2 CH3COO- NH4+ + CO2 + H2O
Displayed formula of CH3COO- NH4+
Refer to booklet man
What does the excess acid prevent?
Show eqn.
(Form amides from carboxylic acids)
- Dissociation of the ammonium salt
RCOONH4 ⇌ RCOOH + NH3
Show the eqn of the ammonium salt dehydrating from heat
RCOONH4 -> RCONH2 + H2O
How would u make nitriles from amides?
Dehydrating the amide (loss of water)
How do u dehydrate the amide?
(2-way)
- Heating solid mixture of amide
- w/ phosphorus(V) oxide (P4O10)
“In-depth detail” of making nitrile from amide?
(3-way)
- Water removed from amide group
- Leaves a nitrile group, -CN
- Liquid nitrile collected by simple distillation
Show eqn of gaining ethanenitrile by dehydrating ethanamide
State reagent used
(Whiteboard)
CH3CONH2 + P4O10 -> CH3CN + H2O
REAGENT = Phosphorus(V) oxide aka P4O10
What group is nitrile?
-C≡N group
How do u introduce a cyanide ion into a halogenoalkane?
Thru nucleophilic substitution
How do u introduce a cyanide ion into a carbonyl compound?
Thru nucleophilic addition
What do both nucleophilic addition/substitution provide a means of?
(Nitriles from halogenoalkanes)
(2-way)
- Increasing the length
- of a carbon chain in an organic molecule
What condition is required to introduce a cyanide ion into a halogenoalkane?
Refluxed w/ ethanolic potassium cyanide
Eqn for halogenoalkane refluxed with ethanolic potassium cyanide
State what type of mechanism it is.
(Whiteboard)
RCH2I + KCN -> RCH2CN + KI
Nucleophilic substitution
Draw the mechanism for halogenoalkane refluxed with ethanolic potassium cyanide
(It’s kinda similar…)
(Whiteboard)
The honors are yours
If u add HCN to ethanal/propanone, what’s that mechanism called?
Nucleophilic addition
What is the rate and how do u increase it?… for the addition of HCN to ethanal/propanone?
- Slow
- Increases by addition of alkali/cyanide ions
How does adding alkali for the addition of HCN to ethanal/propanone greatly increase rate?
(2-way)
- Neutralises some of the HCN molecules
- giving higher conc. of cyanide ions
Equation of addition of HCN to ethanal/propanone?
(Whiteboard)
H3C-C(=O)-H + HCN/KCN -> H3C-CH(OH)-CN
Mechanism of addition of HCN to ethanal/propanone?
(Do ethanal insteada propanone)
(Whiteboard)
Refer to the booklet
What can only rotate plane polarised light?
(3 things, or whatever comes to ur mind)
- Enantiomers
- Racemic mixture
- Chiral centre
What are 2 other hydrolysis’ other than normal hydrolysis?
- Acid hydrolysis
- Alkali/Base hydrolysis
What happens if u do alkali/base hydrolysis towards ethanenitrile?
(2-way)
- Gain solution containing ethanoate ions
- and ammonia
Equation of alkali/base hydrolysis towards ethanenitrile?
H3C-C≡N -> H3C-C(=O)O-Na + NH3
-> = NaOH(aq)
What’s the 2nd step to gaining the carboxylic acid after step 1 of alkali/base hydrolysis towards ethanenitrile?
(3 things)
- Liberate the “weak acid”
- Supply enough hydrogen ions from a strong acid (HCl)
- Enough to the mixture = acidic
What’s the difference with alkali/base hydrolysis?
(2 things)
- It is a two-step reaction
- Produces a salt first
What happens if u do acid hydrolysis towards ethanenitrile?
(2 things)
- You gain an ethanoic acid
- almost similar to normal hydrolysis
Even if u do acid hydrolysis, how would u gain just the carboxylic/ethanoic acid?
Distill off the mixture
How is acid hydrolysis performed towards ethanenitrile?
(2-way)
- Nitrile heated under reflux
- with dilute acid (e.g. dilute hydrochloric acid)
Equation of acid hydrolysis towards ethanenitrile?
(Whiteboard)
H3C-C≡N -> H3C-C(=O)OH + +NH4
-> = (H+/H2O) or (HCl(aq))
What other group can also be converted into their corresponding carboxylic acid likewise?
Amides
(NH2)
How is acid hydrolysis performed + results towards ethanamide?
(2 things + 2-way)
- Heat with dilute acid (e.g. HCl)
- Ethanoic acid formed tog. with ammonium ions
- If use HCl, final solution =
- ammonium chloride & ethanoic acid
Eqn of acid hydrolysis towards ethanamide?
(Whiteboard)
CH3CONH2 -> CH3COOH + NH4+Cl
-> Above = HCl(aq)
-> Below = △, (+ H2O + HCl)
Draw the displayed formula of the eqn of acid hydrolysis towards ethanamide
(Whiteboard)
U got it
How about alkaline/base hydrolysis towards amide?
(4 thingies)
- Amide heating with NaOH
- Ammonia gas given off
- Left with solution of sodium ethanoate
- Exactly like with nitriles w/ 2 steps to gain carboxylic acid
Eqn of alkaline/base hydrolysis towards amide
(Whiteboard)
CH3CONH2 + NaOH -> CH3COO -Na + NH3 -> CH3COOH
2nd -> = HCl(aq)
Rando as hell but, list 2 things lithium aluminium hydride (LiAlH4) can convert?
- Carboxylic acid -> 1° alcohol
- Nitrile -> amine
Difference between amine + amide?
Amine = NH2
Amide = C(=O)NH2
Thus, what’s the reagent used to reduce nitriles to primary amines (CH3-NH2)?
- Lithium aluminium hydride
- Lithium tertahydridoaluminate(III)
- LiAlH4
Show simple equation formula for the reduction of nitriles?
(Whiteboard ig)
CH3CH2CN -> CH3CH2CH2NH2
aka
Propanenitrile -> Primary amine (propylamine)
Show the eqn of the reduction of butanenitrile using lithium aluminium hydride
(Whiteboard)
CH3CH2CH2CN + 4 [H] -> CH3CH2CH2CH2NH2
But.. why it no say LiAlH4?
Sorry but, refer to booklet at the back for reducing agents strength…. otherwise…. which ones generally stronger?
Sorry sorry, ease of reduction
But ofc, it’s the LiAlH4
U finished it…..? Test is monday, and look at ur situation rn ,’:)
Yeahhh i don’t rlly want to plan my demise at least….
