PH1125 - Amines & Carboxylic acids Flashcards
what is an amine? (2)
- organic compounds containing trivalent N atoms bonded to one or more carbon atoms
- RNH2 / R2NH / R3N
how is the classification of an amine determined?
- depending on the number of alkyl/aryl substituents attatched to the nirtogen
what is an amine salt? (2)
- there are 4 bond coming from N
- one or more of the attachements is H
what is a quaternary ammonium salt?
- if all 4 groups are alkyl/aryl (ie no H on the N)
what are the methods and mechanisms for the preparation of an amine?
- nucleophilic substitution; RX + NH3 → RNH3+X- (by Sn2 reaction) then addition of -OH to form amine
- reduction; amide/nitrile → RCH2NH2 (addition of reducing agent)
- amide rearrangement; halogen and base (-OH) is added
mechanism of alkyl halide to amine? (2)
- ammonia/amine + alkyle halide → amine salt + halide ion (by Sn2 reaction)
- amine salt + base (eg NaOH) → amine ( + water + Na-halide)
how are nitriles often obtained?
- from an Sn2 reaction including alkyl halides and cyanide
mechanism of reductive amination? (3)
- nucleophilic attack by NH3 at the carbonyl C - intermediate carbinolamine
- loss of water to form an imine
- imine reducedby H2/Raney nickel to form primary amine
what drug is commonly prepared commercially by reductive amination?
- amphetamines
what are the two reactions that amines can undergo? (2)
- acylation
- hofmann elimination
what are amines acylatd by to give amides? (2)
- acid chlorides
- acid anhydrides
mechanism of amine acylation to form amide? (3)
- C=O bond curl arrow to O and lone pair in N of amine to C of acid chloride
- O- (from double bond that just broke) to bond and C-Cl bond to Cl
- N-H bond curly arrow to N+ and Cl- (that just came off) to H on N
what is the hofmann elimination reaction? (2)
- quaternary ammonium salts can be converted into amide and alkenes on heating
- reaction occurs via an elimination reaction (E2)
what is the hofmann product and why? (2)
- the least substituted alkene (simplest)
- owing to steric hinderance in the transition state
where does the acidity in carboxylic acids come from?
- resonance stabilisation of carboxylate ion
- the greater the stabiliation, the greater the acidity
what is a carboxylic acid dimer?
- two H boned carboxylic acids
what are the methods of preparing a carboxylic acid? (3)
- ester + water → carboxylic acid + alcohol
- amide + water → carboxylic acid + amine
- nitrile + water → carboxylic acid + ammonia
what is the mechanism of base-induced ester hydrolysis? (ester + alkyl) (4)
- double bond curly arrow to O and nucleophile (eg -OH from sodium hydroxide) -ve charge to C (this form an alkoxide intermediate)
- intermediate then forms R-COOH group and -OR
- -OR to H in carboxylic acid functional group and OH bond curly arrow to O; this forms R-COO- and HOR
- dilute acid (H3O+) is added to form carboxylic acid
what reagent is used the oxidation of primary alcohols and what are the products? (2)
- jones reagent (strong oxidising agent)
- primary alcohol → aldehyde → carboxylic acid
what is the jones reagent?
- CrO3 + H2SO4 → H2CrO4
what do aldehydes require to form carboxylic acids? (2)
- mild oxidising agents (eg tollens)
- Ag+(NH3)
how would you convert carbon dioxide to a carboxylic acid (4)
- grignard carboxylation with R-MgBr
- C=O double bond curly arrow to O and R-MgBr bond to C
- formation of C-COO- and +MgBr
- dilute acid (H3O+) added to form carboxylic acid
what is an alpha carbon?
- the carbon adjacent to a functional group
what are anions?
- weak bases that can act as nucleophiles
how can esters be formed from anions?
- reaction between reactive alkyl halide and carboxylate anion to produce an ester and the halide ion
- this is an Sn2 reaction
carboxylic acid to alcohol? (2)
- LiAlH4 and H3O+
- reduction
what products can be formed from the nucleophilic substitution of a carboxylic acid? (4)
- acid chloride
- anhydride
- ester
- amide
※ conversion of hydroxy group into a good leaving group
carboxylic acid to acid chloride?
- SOCl2
carboxylic acid to acid anhydride?
- carboxylic acid (nucleophile) and acid chloride
synthesis of aspirin?
- salicylic acid + acetic anhydride + acid (H+)
carboxylic acid to ester mechanism? (4)
- activation of C=O
- nucleophilic addition
- transfer of proton converting OH to H2O (improvement of leaving group)
- loss of H2O and regeneration of H+
how would you convert an amide to a carboxylic acid and amine? (2)
- hydrolysis
- H+ and H2O
how would you convert an amide to amine? (2)
- reduction
- LiAlH4
