Chemical Tests/ Reactions

How to test for optical isomerism?

Pass Plane Polarized light through mix/compound

Result of test for optical isomerism

No rotation = negative for optical isomerism or racemic mixture

What type of reaction are the nitration of benzene, the halogenation of benzene and the Friedel-Crafts alkylation of benzene?

Electrophilic addition/substitution

what are the 3 steps of Nitration of Benzene?

1. Preparing the Electrophile
2. Electrophilic attack
3. Regeneration of the catalyst

What reagents/conditions are needed for the nitration of Benzene

Concentrated sulfuric acid and concentrated nitric acid

Which reagent is the catalyst in the nitration of benzene?

Concentrated sulfuric acid (nitric acid needed for formation of NO2+)

What catalyst is required for the chlorination of benzene?

Anhydrous aluminium chloride (AlCl3)

What conditions are required for Chlorination of Benzene?

Reflux in presence of halogen carrier

What catalyst is required for the bromination of benzene?

Iron (|||) Bromide (FeBr3)

What is the purpose of the catalyst in bromination of benzene?

Polarise bromine

What is Friedel Crafts alkylation?

Reaction of benzene with chloroalkane

What catalyst is needed for Friedel-Crafts alkylation?

anhydrous Aluminium Chloride (AlCl3)

What are the two problems with the Friedel - Crafts reaction?

polyalkylation and carbocation arrangement

Important Friedel - Crafts style reaction

Manufacture of phenylethene (styrene)

Reagents for Step 1 - Phenol + Ethene

HCl + AlCl3

Result of step 1 - Phenol + Ethene

Phenylethane

Reagents and conditions for Step 2 - Phenylethane

ZnO + 630’C

Results of Step 2 - Phenylethane

Phenylethene formed

How is phenol produced?

Forced conditions (not environmentally friendly) - addition of sodium hydroxide (NaOH) to chlorobenzene at 300'C and increased pressure

Is phenol acidic or basic in regards to litmus paper?

Acidic - turns blue litmus paper red (1)

How to test for an acid?

Add NaHCO3

Result of test for acid?

Positive test shows effervescence (CO2)

What reagents are needed for the formation of alcohols from Halogenoalkanes?

Aqueous solution of an alkali (NaOH/KOH)

What conditions are needed for the formation of alcohols from Halogenoalkanes?

Heated under reflux

What type of reaction is the formation of alcohols from halogenoalkanes?

Nucleophilic substitution

What reagents are needed for the formation of alcohols from alkenes?

Phosphoric acid supported on silica (catalyst)

What conditions are needed for the formation of alcohols from alkenes?

300'C 60-70atm

What reagents are needed for the formation of alcohols from the reduction of an aldehyde?

NaBH4 in water or LiAlH4 in dry ether (reducing agents)

What reagents are needed for the formation of alcohols from the reduction of a ketone?

NaBH4 in water or LiAlH4 in dry ether

What reagents are needed for the reaction of alcohols with hydrogen bromide?

Sodium bromide and concentrated sulfuric acid

What conditions are needed for the reaction of alcohols with hydrogen bromide?

Heat NaBr and H2SO4 to prepare nucleophile (in situ)

Why is cH2SO4 used in the reaction of alcohol and HBr?

Used to make HBr, as a catalyst and as a dehydrating agent

What reagents are needed for the reaction of alcohols with hydrogen chloride?

(Only for tertiary alcohols) same method as hydrogen bromide

What reagents are needed for the reaction of alcohols with hydrogen iodide?

NaI/KI and concentrated Phosphoric acid (H3PO4)

What reagents are needed for the reaction of alcohols with HCl and ZnCl2?

passing HCl gas into alcohol in presence of anhydrous zinc chloride catalyst

What conditions are needed for the reaction of alcohols with HCl and ZnCl2?

Heat

What reagents are needed for the reaction of alcohols with Phosphorous (v) chloride?

PCl5

What is formed in the reaction of an alcohol with Phosphorous (v) chloride?

chloroalkane, phosphoryl chloride (POCl3) and HCl gas

What reagents are needed for the reaction of alcohols with sulfur dichloride?

SOCl2

What is formed in the reaction of an alcohol with sulfur dichloride?

chloroalkane, sulfur dioxide (SO2) and HCl gas

What reagents are needed for the reaction of alcohols with Phosphorous (||) iodide?

PI3 (made by warming damp red phosphorus and iodine)

What is formed in the reaction of an alcohol with Phosphorous (||) iodide?

iodoalkane and H3PO3

What reagents are needed for the oxidation of a primary alcohol?

Acidified potassium dichromate (K2Cr2O7) or Potassium permanganate (KMnO4) and dilute sulfuric acid (H2SO4)

What conditions are needed to oxidise a primary alcohol to an aldehyde?

Gently heated with K2Cr2O7 and remove aldehyde from mixture by distillation after it's formed

What conditions are needed to oxidise a primary alcohol to a carboxylic acid?

Reflux with excess acidified potassium dichromate (don't distill after aldehyde is formed) or use potassium permanganate (KMnO4)

What colour change is observed when using acidified potassium dichromate to oxidise an alcohol?

Orange to green

What colour change is observed when using potassium permanganate to oxidise an alcohol?

Purple to colourless

What do secondary alcohols oxidise to?

Ketones

What do tertiary alcohols oxidise to?

Nothing, they do not undergo oxidation

What does the dehydration of an alcohol form?

alkene

What reagents are needed to dehydrate alcohols?

Concentrated sulfuric acid or Aluminium oxide

What conditions are needed to dehydrate an alcohol?

Heat alcohol with dehydrating agent

What is used to test for the presence of a double bond in a molecule?

Bromine water

What colour change is observed if a double bond is present?

Orange/brown to colourless

What reagents are needed to form an ester from alcohols and carboxylic acids?

concentrated sulfuric acid (H2SO4)

What conditions are needed to form an ester from alcohols and carboxylic acids?

Heat

How can esterification reactions be used to test for an alcohol?

Addition of sulfuric acid to an alcohol produces a sweet smelling ester

What reagents/conditions are needed to form an ester from alcohols and acyl chlorides?

Mix together at room temperature - no catalyst is needed

What reagents are needed for the reaction of phenol with bromine?

Bromine (Br2) and no catalyst required

What type of reaction is the reaction of phenol and bromine?

electrophilic substitution

What is formed in the reaction between phenol and bromine?

2,4,6-Tribromophenol

What color change is observed when phenol reacts with bromine water?

orange to white precipitate

What color change is observed when phenol reacts with Iron (|||) Chloride (FeCl3)?

Pale yellow to deep purple/violet or red/green

What reagents are needed for the esterification reaction between a phenol and an acyl chloride?

Pyridine catalyst

What reagents are needed in the silver mirror test?

Tollen's reagent - Silver nitrate \[Ag(NH4)2\]+ in aqueous ammonia

Conditions required for silver mirror test

Heat with aldehyde

What is formed in the silver mirror test?

Carboxylic acid + silver compound

Metallic silver = silver mirror

What does the sliver mirror test do?

distinguishes between aldehydes and ketones

What molecule gives a positive silver mirror test?

aldehyde

What test for an aldehyde gives a color change of blue to brick red?

boil with Fehling's solution

What is formed in Fehling’s solution test

Carboxylic acid + Cu2+ → Cu2O = brick red precipitate

What type of reaction is the 2,4-DNPH test?

condensation reaction/nucleophilic addition elimination

What does 2,4-dinitrophenylhydrazine test for?

aldehydes and ketones

What does a positive 2,4-DNPH test give?

Orange crystalline product

What chemical test is used to check for a methyl group attached to the first carbon of an aldehyde, ketone, primary or secondary alcohol?

Triiodomethane/iodoform reaction

What reagents are needed for the iodoform reaction?

Iodine in sodium hydroxide or mix of potassium iodide and sodium chlorate

What color is observed in a positive iodoform test?

pale yellow precipitate

What is formed in the iodoform rxn that produces the pale yellow ppt?

CH3I

What type of reaction is the reaction of an aldehyde/ketone with hydrogen cyanide?

nucleophilic addition

What reagents are needed in the reaction of an aldehyde or ketone with hydrogen cyanide?

dilute sulfuric acid in aqueous solution of aldehyde or ketone dissolved in potassium cyanide

What is formed in the reaction of aldehydes/ketones with HCN

Cyanohydrins

Why is the rxn of aldehyde/ketone with HCN useful?

Nitrile group can undergo hydrolysis in acid conditions (reflux with any dilute acid) to form a carboxylic acid group

Is a carboxylic acid acidic or basic in regards to litmus paper?

Acidic - turn blue litmus paper red (2)

What reagents are needed for the reduction of a carboxylic acid?

LiAlH4

What reagents are needed for the formation of an aromatic carboxylic acid from an alkylbenzene?

KMnO4 in alkaline NaOH to form a benzene carboxylate ion and dilute H2SO4 to form benzoic acid

Why is sulfuric acid needed to form an aromatic carboxylic acid?

Catalyst, adds proton and product = salt of acid b/c conditions = alkaline + mix must be acidified with HCl to free acid

What conditions are needed for the formation of an aromatic carboxylic acid?

Reflux

What colour change is observed in the formation of an aromatic carboxylic acid?

Purple to Dark brown precipitate

What reagent is needed for decarboxylation?

Sodalime (mix of NaOH, CaO and Ca(OH)2)

What reagents are needed for the formation of an acid chloride from a carboxylic acid?

Thionyl chloride (SOCl2)(preferred) or PCl3/PCl5

What does the Hydrolysis of an ester give?

corresponding alcohol and carboxylic acid

What does the hydrolysis of an acid chloride give?

carboxylic acid and 'fuming' hydrogen chloride gas

What reagents are used in acid hydrolysis of an ester?

H2O in presence of a dilute acid

What reagents are used in alkaline hydrolysis of an ester?

Sodium hydroxide

To produce a carboxylic acid in alkaline hydrolysis, what additional reagents is needed and why?

dilute acid to hydrolyze salt formed

What reagent is needed for the formation of an amide from an acid chloride?

Ammonia (NH3)

What reagents/conditions are needed in step one of the formation of an amide from a carboxylic acid?

Ammonia (NH3) or ammonium carbonate ((NH4)2CO3)

What reagents/conditions are needed in step two of the formation of an amide from a carboxylic acid?

heat strongly to dehydrate salt and make amide

What reagents/conditions are needed to dehydrate an amide to form a nitrile?

Phosphorous (V) oxide (P4O10) and heat

what reagents are needed to form a nitrile from a halogenoalkane?

potassium cyanide (KCN) dissolved in ethanol