Module 6: Carbonyls, Carbocylic Acid, Acyl And Esters Flashcards by Shona Mallen

Carbonyls
What are carbonyl compounds

Aldehydes and ketones

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Carbonyls
What is the carbonyl functional group

C=O

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Carbonyls
Where is the carbonyl group in aldehydes

At end of chain

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Carbonyls
What is aldehydes suffix

-al

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Carbonyls
Where is the carbonyl group in ketones

In middle of group

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Carbonyls
What is the suffix for ketones

-one

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Carbonyls
How are carbonyls made

Oxidising alcohols

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Carbonyls
What is used to oxidise alcohol s

Oxidising agent acidified potassium dichromate H+/K2Cr2O7

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Carbonyls
How do you form an aldehyde

Partially Oxidise a primary alcohol in distillation

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Carbonyls
How do you form a ketone

Fully oxidise a secondary alcohol in reflux

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Testing for carbonyl compounds
What is used to test

2,4-DNP

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Testing for carbonyl compounds
What does 2,4-DNP detect

Prescience of carbonyl functional group in aldehydes and ketones

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Testing for carbonyl compounds
What is observed when 2,4-DNP in presence of carbonyl

Yellow-orange precipitate is formed

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Testing for carbonyl compounds
How is 2.4-DNP used in practical

Dissolved in methanol and sulfuric acid as asa a solid is very hazardous and explosive

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Testing for carbonyl compounds
What is 2,4-DNP

2,4-dinitrophenylhydrazine

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Testing for carbonyl compounds
Practical method for testing carbonyls

Add 5cm 2,4-DNP solution to clean test tube this is in excess
Use pippete add 3 drops of unknown compound and leave to stand
Is no yellow crystals form add few drops of sulfuric acid
A yellow orange precipitate indicates presence of group

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Testing for carbonyl compounds can 2,4-DNP test for carboxylic acid

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Testing for carbonyl compounds
How can you identify compounds using 2,4-DNP

Orange precipitate is a derivative of carbonyl compounds each different produces a crystalline precipitate with a different melting point so can measure melting point and compare to known

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Testing for carbonyl compounds
How can you distinguish between aldehyde and ketone

Using tollens reagent

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Testing for carbonyl compounds
What does the tollens reagent use to distinguish

Fact that an aldehyde can be easily oxidised to a carboxylic acid and a ketone cannot

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Testing for carbonyl compounds
What is tollens reagent

Clear solution of silver nitrate in aqueous ammonia

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Testing for carbonyl compounds
What happens to tollens reagent in prescience of aldehyde

Silver mirror is formed

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Testing for carbonyl compounds
Practicals for tollens reagent

In clean test tube add 3cm^3 aqueous silver nitrate
Add aqueous silver hydroxide to test tube until a brown precipitate of silver oxide is formed, Ag2O
Add dilute ammonia solution until brown precipitate just dissolves to form a clear colourless solution this is tollens
Pour 2 cm depth of unknown solutions to clean test tube
Add equal volume of tollen
Leave test tube to stand in beaker of warm water about 50’C for 10-15 mins then observe if silver mirror formed

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Testing for carbonyl compounds
Ionic equation for use of tollens

Ag(NH3)2+ (aq) + e- —> Ag(s) + 2NH3 (aq)

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Reactions of carbonyls How can you change carbonyls ack to alcohols

Reduction

Reactions of carbonyls What is used to reduce carbonyls (general)

Reducing agent

Reactions of carbonyls What symbol represents reducing agent

[H]

Reactions of carbonyls What are aldehydes reduced to

Primary alcohol

Reactions of carbonyls Equation for reducing aldehyde

RCHO + 2[H] —> RCH2OH

Reactions of carbonyls What are ketones reduced to

Secondary alcohol

Reactions of carbonyls Equation for reducing ketone

RCOR’ + 2[H] —> RCHOHR’

Reactions of carbonyls What reducing agent is often used

NaBH4 dissolved in water with methanol (Sodium borohydride

Reactions of carbonyls What kind of reaction is reduction

Nucleophilic additons

Reactions of carbonyls Why is reduction nucleophilic addition

Nucleophile attacks molecule and extra group is added

Reactions of carbonyls Description of mechanisms for recution

Reducing agent supplied hydride ions H- which has a lone pair of electrons so its a nucleophile and can attack the delta positive carbon on carbonyl group Electron pair from C=O moves onto o making it -ve Lone pair of oxygen removes proton from water and over there is addition of hydrogen

Reactions of carbonyls What ions the other common reaction

Hydrogen cyanide

Reactions of carbonyls What does hydrogen cyanide and carbonyls produce

Hydroxynitrile molecules (with -OH and -CN group )

Reactions of carbonyls What type fo reaction is carbonyl and hydrogen cyanide

Nucleophilic addition

Reactions of carbonyls What is hydrogen cyanide so what’s does it do in water

Weak acid so partially dissolves to form H+ and CN- ion s

Reactions of carbonyls Partial dissociation of HCN

HCN <=> H+ + CN-

Reactions of carbonyls Mechnaism for reaction with HCN

CN- ion attacks slightly positive carbon atom and donates a pair of electrons to it both electrons from double bond transfer to oxygen H+ bond to oxygen to form hydroxyl group

Reactions of carbonyls What is true for HCN

Highly toxic gas

Reactions of carbonyls How is HCN used in laboratories

Solution of acidified hydrogen cyanide in fume cupboard

Reactions of carbonyls For reduction what is the condition

Aqueous or alcoholic

Reactions of carbonyls What is the condions of HCN

Reflux

Reactions of carbonyls Equation for HCN with ethanal

CH3CHO + HCN —> CH3CH(OH)CN

Reactions of carbonyls What is the reaction with HCN useful for

Adding an extra C atom to a chain as CN can then be converted to carboxylic acid or amines

Reactions of carbonyls What is the reaction with HCN useful for

Adding an extra C atom to a chain as CN can then be converted to carboxylic acid or amines

Carboxylic acid What is the functional group

-COOH

Carboxylic acid What are carboxylic acids

Weak acids

Carboxylic acid What happens to carboxylic acid in water

Partially dissociate into carboxylate ions and H+ ions

Carboxylic acid Where does the equilibrium lie in the dissociation

Towards left as most of molecules don’t dissociate

Carboxylic acid What are they often used as

In organic synthesis as starting materials or intermediates to make more useful compunds

Carboxylic acid What is the name of the functional group

Carboxyl group

Carboxylic acid What type of imf can they form

Hydrogen bonds

Carboxylic acid Whycan they form hydrogen bonds

C=O and O-H bond polar and Lone electron pair on oxygen to hydrogen also to water molecules

Carboxylic acid Are they soluble

Yes

Carboxylic acid Why are they soluble

Form hydrogen bonds to water molecules

Carboxylic acid What happens to solubility at number of carbon atoms increase and why

Solubility decreases as non polar carbon chain has a greater effect on the overalll polarity fo the molecule

Carboxylic acid Why are carboxylic acids more soluble then alcohol

Can form two hydrogen bonds for every one molecule with a carboxyl group

Carboxylic acid Are they strong acuds

No weak

Carboxylic acid What happens when dissolved in water

Partially dissociate

Carboxylic acid Partial dissociation of methanoic acid

HCOOH(aq) <==> H+(aq) + HCOO-(aq)

Carboxylic acid reactions What type of reactions do they undergo with what

Redox reactions with metals Neutralisation reactions with bases

Carboxylic acid reactions In redox and neutralisation reactions what do they form

salts

Carboxylic acid reactions Name of salt they form

Carboxylate salts

Carboxylic acid reactions What is the ion called they form.

Carboxylate ion

Carboxylic acid reactions What do aqueous solution react with metals to form

Carboxylate salt and hydrogen gas

Carboxylic acid reactions What would you observe with redox reaction with metal

Metal disappearing and effervescence as hydrogen gas released

Carboxylic acid reactions Reaction for propanoic acid and magnesium

Mg(s) + 2 CH3CH2COOH(aq) —> (CH3CH2COO)2Mg(aq) + H2(g)

Carboxylic acid reactions What do the form from reacting with metal oxide

Metal carboxylate salt and water

Carboxylic acid reactions Reaction for Ethanoic acid and calcium oxide

CaO(s) + 2 CH3COOH(aq) —> (CH3COO)2Ca(aq) + H2O(l)

Carboxylic acid reactions What dot form from reaction with alkali

Salt + water

Carboxylic acid reactions Ionic equation for acid and alkali

H+(aq) + OH-(aq) —> H2O

Carboxylic acid reactions Observation for reaction with alkali

May not see reaction as for an aqueous solution of salt

Carboxylic acid reactions What is formed from reaction with carbonate

Metal carboxylate salt + water + CO2 gas

Carboxylic acid reactions Observation for reaction with carbonate

If carboxylic acid is in excess, solid carbonate would disapppear and effervescence from co2

Carboxylic acid test What is used to test for carboxylic acids

Neutralisation reaction with carbonates

Carboxylic acid test Why can they reaction with carbonates be used to test for it

Only common organic compounds sufficiently acidic enough to react with carbonates

Carboxylic acid test What is the carbonate test specifically useful to distinguish from

Phenol as they’re not acidic enough you react with carbonates

Esters What is the functional group

R-COO-R

Esters What is the name made up of

Alcohol sections is first part eg ethanol becomes ethyl Carboxylic acid derivative is the second part eg Ethanoic acid becomes ethanoate

Esters What s the name of the Esther from propanol and butanoic acid

Propyl butanoate

Esters What is a carboxylic acid derivative

Something that can be made from carboxylic acid eg acrylic chloride

Esters What type of reaction si esterification

Equilibrium

Esters What is esterificaiton

Making esters from carboxylic avid and alcohol

Esterification What are the reactants

Alcohol + carboxylic acid

Esterification What are the conditions

Reflux and conc acid catalyst (conc H2SO4 or H3PO4)

Esterification What does it produce

Ester and water

Esterification Where do the oxygens on the ester come from

C=O oxygen comes from carboxylic avid C-O-C exogenous comes from alcohol Other oxygen and 2 H form H2O

Esterification What type of reaction is this an example of and why

Condensation as molecules combine by releasing a smaller molecule

Esterification What does conc H2SO4 acts as and why

Dehydrating agent as removes water

Esterification What does the conc H2SO4 do for equilibrium

Removes water causing POE to move to right increasing yield of ester and water

Esterification What does the reaction being reversible mean

Product need to be separated as formed

Esterification How can you separate smaller esters as formed and why

Warm and distil them off a more volatile than other compounds

Esterification Esterification How can you separate larger esters and formed and why

Harder to form so best to heat them under reflux and use fractional distillation

Esterification Equation for ethanol and Ethanoic acid

CH3CH2OH + H3CCOOH <==> CH3CH2OOCCH3 + H2O

Esterification Wgat are two other ways to form esters

From alcohols and acid anhydrides From alcohols and acrylic chlorides

Esterification What are acid anhydrides

Made from two carboxylic acids

Esterification Equation for two Ethanoic acids

2 H3CCOOH —> CH3C(=O)O(O=)CCH3 + H2O

Esterification Conditions for acid anhydrides + alcohol

Heat

Esterification What is the products of acid anhydrides + alcohols

Ester + carboxylic acid

Esterification How are the ester and carboxylic acdi separated

By fractional distillation

Esterification Equation for Ethanoic anhydride + methanol

H3CC(=O)O(O=)CCH3 + CH3OH —> H3CC(=O)OCH3 + CH3COOH

Esterification What is the products from acrylic chloride and alcohol

Ester + hydrogen chloride

Esterification Equation for ethyl chloride + methanol

CH3C(=O)Cl + CH3OH —> CH3C(=O)OCH3 + HCl

Hydrolysis of ESters What are the two types of hydrolysis

Acid hydrolysis Base hydrolysis

Hydrolysis of ESters What is used in both hydrolysis

water

Hydrolysis of ESters What does acid hydrolysis split ester into

Carboxylic Acid and alcohol

Hydrolysis of ESters Conditions for acid hydrolysis s

Reflux with dilute acid such as HCl or H2SO4

Hydrolysis of ESters Equation for acid hydrolysis of ethyl ethanoate

CH3C(=O)OCH2CH3 + H2O <=> CH3COOH + CH3CH2OH

Hydrolysis of ESters Is acid hydrolysis reversible

Yes

Hydrolysis of ESters What is the problems of acid hydrolysis

Reversible reaction so will start to return to reactants

Hydrolysis of ESters What is used to pushy equilibrium to products

Need to add lots of water

Hydrolysis of ESters What is produced in base hydrolysis

Carboxylate salt + alcohol

Hydrolysis of ESters What are the conditions for base hydrolysis

Reflux with dilute alcohol

Hydrolysis of ESters Is base hydrolysis reversible

Hydrolysis of ESters Equation for ethyl ethanoate + NaOH

CH3C(=O)OCH2CH3 + NaOH —> CH3COO- Na+ + CH3CH3OH

Hydrolysis of ESters After base hydrolysis how can the carboxylic avid be reformed and what will be formed

Add HCl to products mixture The carboxylic acid + metal chloride salt

What are the two carboxylic acid derivative need to know

Acyl chlorided Acid anhydrides

Acyl chlorides What is the functional group

-COCl

Acyl chlorides What is the general formula

CnH2n+1COCl

Acyl chlorides What do they all end in

-oyl chloride

Acyl chlorides What is import about the functional group

Two dipoles on carbon from C=O bond and C-Cl

Acyl chlorides What is the slightly positive carbon atom susceptible for attach from

Nucleophiles

Acyl chlorides Why are they susceptible to attack from nucleophiles

Positive carbon due to 2 electron with drawing groups

Acyl chlorides What type of reactions do they undergo

Nucleophilic Addition elimination

Acyl chlorides What is their relative reactivity

Much more reactive then carboxylic acids and acid anhydrides

Acyl chlorides How do you form them

Chlorinations of carboxylic acids

Acyl chlorides What does chlorination of carboxylic acids involve

Replacing -OH with -Cl

Acyl chlorides What two reagents could possible be used for chlorinations of carboxylic acids

Thionyl chloride (SOCl2) to phosphorus pentachloride (PCl5)

Acyl chlorides What conditions are needed for chlorination of carboxylic acid

Dry conditions

Acyl chlorides What is produced in chlorinations of carboxylic acid using thionyl chloride

Acyl chloride + SO2 + HCl

Acyl chlorides What is the equation for Ethanoic acid and thionyl chloride

CH3COOH + SOCl2 —> CH3COCl + SO2 + HCl

Acyl chlorides What are the four nucleophiles they react with

Water Alcohol Ammonia Amine

Acyl chlorides What is produced in reaction with water

Carboxylic acid + HCl(g)

Acyl chlorides Equation for ethanoyl chloride and water

CH3COCl + H2O —> CH3COOH + HCl(g)

Acyl chlorides What is produced in reaction with alcohol

Ester and HCl

Acyl chlorides Equation for ethanoyl chloride and ethanol

CH3COCl + CH3CH2OH —> CH3COOCH2CH3 + HCl(g)

Acyl chlorides What is produced with ammonia

Primary amide and HCl

Acyl chlorides What is reaction of ethanoyl chloride and ammonia

CH3COCl + NH3 —> CH3CONH2 + HCl

Acyl chlorides What is produced with amine

Secondary amide and HCl

Acyl chlorides Equation for ethanoyl chloride and methyl amine

CH3COCl + CH3NH2 —> CH3CONHCH3 + HCl(g)

Acyl chlorides What is always produced in Acyl chloride reactions

HCl gas

Acyl chlorides What is observed in Acyl chloride reactions and what is this useful for

White fumes from gas HCl useful to identify Acyl chlorides

Acyl chlorides Why are Acyl chlorides not always used (2)

HCl produced which is corrosive Extremely exothermic and releases lots of heat

Acyl chlorides Why are Acyl chlorides sometimes chosen to be used

More reactive so less energy needed and cheaper

Acyl chlorides At what temp for these reactions occur

RTP

Acid anhydrides What is the functional group

R-C(=O)O(O=)C-R

Acid anhydrides How do you name them

-anoic anhydride

Acid anhydrides Relative reactivity

Less reactive

Acid anhydrides What does produce with water

2 carboxylic acid

Acid anhydrides Equation for Ethanoic anhydride with water

CH3COOOCCH3 + H2O —> 2CH3COOH

Acid anhydrides What is produced with alcohol

Ester and carboxylic acid

Acid anhydrides Eqatuoin for Ethanoic anhydride and ethanol

CH3COOOCCH3 + CH3CH2OH —> CH3COOCH2CH3 + CH3COOH

Acid anhydrides What is produced with ammonia

Primary amide and carboxylic acid

Acid anhydrides What is equation for Ethanoic anhydride and ammonia

CH3COOOCCH3 + NH3 —> CH3CONH2 + CH3COOH

Acid anhydrides What is rpdocued with amine

Secondary amide and carboxylic acid

Acid anhydrides Equation for Ethanoic anhydride and methyl amine

CH3COOOCCH3 + CH3NH2 —> CH3CONHCH3 + CH3COOH

Acid anhydrides Why might these be prefered over Acyl chloride

Less reactive so less exo producing less heat Doesn’t proceed HCL only carboxylic acids

Acid anhydrides Why is carboxylic acid preferred to be reduced then HCl

Are weak acids so less corrosive due to being more soluble as they’re dimers