Unit 4 reactions Flashcards
Preparation of alcohols
From alkenes (60atm, 300C, electrophillic addition, steam hydrolysis)
By fermentation
From halogenoalkanes (reflux with aq NaOH, nucleophillic substitution)
By reduction of carbonyl compounds (primary alcohols from aldehydes, secondary alcohols from ketones, reflux, reducing agent = NaBH4)
By reduction of carboxylic acids (LiAlH4 dissolved in ether, RT, dry)
Reactions of alcohols
Oxidation (primary = heat to aldehydes, reflux to carboxylic acids. Secondary = heat to ketones and no further oxidation. Acidified potassium dichromate (VI) oxidising agent)
Dehydration (170C, elimination, conc. H2SO4, alkene + water)
With ethanoyl chloride CH3COCl (ester + HCl, RT, dry, fume cupboard (HCl forms)
With hydrogen halides:
Iodination: warm damp red phosphorus + iodine = PI3. React PI3 with the alcohol = iodoalkane + H3PO3
Chlorination: HCl gas, ZnCl2 catalyst, heat, nucleophillic substitution, chloroalkane + H2O product
Bromination: “in situ”, KBr, H2SO4, heat, products = bromoalkane, KHSO4 + H2O
Phenol reactions
With bromine (cold, no catalyst, aqueous solution, white ppt + antiseptic smell, electrophillic substitution, + HBr)
With ethanoyl chloride (RT, dry, ester + HCl forms, base e.g - Pyridine C5H5N catalyst)
Preparation of aldehydes and ketones
Aldehydes from the oxidation of primary alcohols (+H2O)
Ketones from the oxidation of secondary alcohols (+H2O)
Acidified potassium dichromate (VI)
Reactions of aldehydes and ketones
Reduction (to alcohols, NaBH4 or LiAlH4 reducing agent, aldehydes to primary alcohols, ketones to secondary alcohols)
Oxidation (only aldehydes, Tollen’s reagent = silver mirror, Fehling’s reagent = blue solution to red ppt)
With 2,4 - DNPH (orange/yellow solid, aqueous solution (not dry), addition-elimination (condensation)
With HCN (nucleophillic addition, the product can be hydrolysed by refluxing with dilute H2SO4 to give a hydroxy acid (CN replaced with COOH)
Iodoform test (I2 + NaOH, yellow crystalline solid CHI3 = iodoform, faint antiseptic smell, positive test with 2-ols, 2-ones, ethanol and ethanal)
Preparation of carboxylic acids
Oxidation of primary alcohols (reflux, acidified potassium dichromate (VI), heat = aldehyde, reflux = carboxylic acid)
Hydrolysis of nitriles (reflux, dilute HCl (carboxylic acid + NH4Cl) or aqueous NaOH (1. Salt + NH3, 2. HCl to form free acid)
Hydrolysis of amides (reflux, dilute HCl or aqueous NaOH = same course of reaction as nitriles)
Aromatic carboxylic acid preparation (reflux, hot alkaline (hot sodium carbonate), HCl added to salt, only when we have a methyl side group on the benzene ring = oxidation can occur with potassium manganate (VII)
Reactions of carboxylic acids
Formation of acid chlorides (anhydrous, use PCl3, PCl5 or SOCl2)
Reduction (RT, dry, LiAlH4 dissolved in ether, to primary alcohols)
Esterification (reflux, conc. H2SO4)
Decarboxylation (forms an alkane, heat with soda-lime [Ca(OH)2/NaOH])
Formation of amides (2 stages: 1 - the carboxylic acid is initially reacted with dilute aqueous NH3 = ammonium ethanoate 2- heated = loses water and amide is formed OR heat with urea at 120C)
Formation of nitriles (either: from amides - P3O10, heat, or from halogenoalkanes - reflux, KCN in ethanol = nitrile + KBr)
Reactions of carboxylic acid derivatives
Nitriles: reduction
LiAlH4 = nitriles —> primary amines
or
with sodium/ethanol —> produces a secondary amine as a by-product
Ethanol chloride
HCl eliminated every time, RT, anhydrous
CH3COCl + water —> CH3COOH
CH3COCl + alcohol —> ester
CH3COCl + primary amine —> amide
CH3COCl + phenol —> ester
CH3COCl + NH3 —> amide
Hydrolysis of carboxylic acid derivatives
Esters (reflux, reverse of esterification, acid or base catalysed)
Amides + nitriles (reflux, heated with alkalis or acids - if base catalysed, need to add HCl to form free acid)
Acid chlorides (RT, white misty fumes HCl)
Preparation of amines
Primary aliphatic amines = halogenoalkane + ammonia
Primary aromatic amines - reducing a nitro compound = reflux + reducing agent is a mixture of tin metal and concentrated HCl
Reactions of amines
With ethanoyl chloride (dry, RT, acetylation, CH3CONHCH3 + HCl, white misty fumes, N-methylethanamide (methyl group bonded to the nitrogen atom due to the lone pair of electrons)
With nitrous acid (HNO2)
Aromatic = diazonium salt + H2O
(Diazonium ion = C6H5N2+, which is stable below 10C)
Aliphatic = cold, effervescence (N2), alcohol, N2, H2O
Catalyst for the hydrogenation of alkenes
Platinum/nickel
What is an implication that something is insoluble in water?
It precipitates in it
