H2 Chemistry 18 - Carboxylic Acids

reaction: oxidation

1^o ROH + [O] -> RCOOH + H₂O

r&c: K₂Cr₂O₇/KMnO₄(aq) H₂SO₄(aq), HUR

RCHO + [O] -> RCOOH + H₂O

r&c: K₂Cr₂O₇/KMnO₄(aq) H₂SO₄(aq), heat

obs: purple KMnO₄(aq) turns colourless, orange K₂Cr₂O₇(aq) turns green

Oxidation

r&c: KMnO₄(aq), H₂SO₄(aq), heat

obs: purple KMnO₄(aq) turns colourless

STRONG Oxidation

r&c: KMnO₄(aq), H₂SO₄(aq), heat

obs: purple KMnO₄(aq) turns colourless

acid hydrolysis

r&c: H₂SO₄(aq), heat

OR

alkaline hydrolysis & acid-base rxn

r&c: NaOH(aq), heat to get RCOO^-

THEN HCl/H₂SO₄(aq) to get RCOOH

redox

r&c: Na, K, Mg

obs: effervescence of H₂, H₂ extinguishes lighted splint w/ pop sound

acid-base reaction

r&c: NaOH/KOH/NH₃(aq)

acid-base reaction(RCOOH only FG that reacts w/ CO₃^2-

r&c: Na₂CO₃/NaHCO₃(aq)

obs: effervescence of CO₂, CO₂ forms white ppt w/ limewater

condensation/ nucleophilic acyl substitution

r&c: alcohol, conc. H₂SO₄, heat

RCOOH -> loses -OH, ROH -> loses -H

to form O-C=O(ester) and H₂O(condensation)

formation of ester favoured by excess ROH & removal of H₂O by H₂SO₄

nucleophilic acyl substitution

r&c: PCl5, rtp(POCl₃, HCl) /

PCl3, heat(H₃PO₃) /

SOCl₂, heat(SO₂, HCl)

RCOOH -> -OH subbed by -Cl

reduction

r&c: LiAlH₄(aq), dry ether

RCOOH CANNOT BE REDUCED BY NaBH₄, methanol/ H₂(g), Ni catalyst

Oxidation

r&c: KMnO₄(aq), H₂SO₄(aq), heat under reflux

obs: purple () decolourises, effervescence of CO₂ forms white ppt w/ limewater

Elimination

r&c: conc. H₂SO₄, heat

methanoic acid -> CO(g) + H₂O

ethanedioic acid -> CO₂(g) + CO(g) + H₂O

acid carbonate test(preferred)

acid-base reaction with CO₃^2-

reaction with PCl5, also test +ve with aliphatic ROH

hydrolysis/nucleophilic acyl substitution

r&c: water, rtp

pdt: RCOOH + HCl(aq)(white fumes)

acyl halides MOST susceptible to attack by nucleophiles -> highly electronegative =O and -Cl makes C highly electron-deficient

Condensation/Nucleophilic acyl substitution

r&c: aliphatic ROH, rtppdt: ester + HCl

OR

r&c: phenol in NaOH(aq), rtp

pdt: ester(with benzene ring) + HCl

**REACTION GOES TO COMPLETION(->)

condensation/nucleophilic acyl substitution

r&c: NH₃/ 1^o amine/ 2^o amine, rtp

**NH₃ cannot be (aq), RCOCl will hydrolyse

+NH₃ -> RCONH₂(1^o amide) + HCl

+RNH₂(1^o amine) -> 2^o amide + HCl

+(R)₂NH₂ (2^o amine)-> 3^o amide + HCl

test: add AgNO₃(aq) to a test tube containing RCOCl.

obs: white ppt of AgCl formed immediately

step 1: (aq) hydrolyses RCOCl -> RCOOH + HCl

step 2: HCl dissociates in (aq) to form Cl^-, reacts with Ag⁺ to form AgCl

condensation/nucleophilic acyl substitution

r&c: conc. H₂SO₄, heat

**REACTION IS REVERSIBLE AS C is not as partially +ve, -OH is not a strong leaving group

condensation/nucleophilic acyl substitution

r&c: aliphatic ROH, rtp

OR

r&c: phenol in NaOH(aq), rtp

**REACTION GOES TO COMPLETION

acid hydrolysis(+H₂O)

r&c: H₂SO₄(aq), heat

pdt: get back ur RCOOH & ROH

**REACTION IS REVERSIBLE(slow rxn)

alkaline hydrolysis(+OH^-) aka saponification

r&c: NaOH/KOH(aq), heat

pdt: get back ur RCOOH -> RCOO^- & ROH

**REACTION GOES TO COMPLETION, greater yield upon acidification

reduction

r&c: LiAlH₄, dry ether

pdt: RCH₂OH + ROH

identify ROH produced from hydrolysis(acid/alkaline)

use triiodoform test/ oxidation

w!!!