ch 20: carboxylic acids Flashcards
carboxylic acid
RCOOH - C double bonded to O and single bonded to OH
what is the hybridization of the carbonyl carbon in a carboxylic acid?
sp2
diacid
compounds with 2 COOH groups
physical properties of carboxylic acids
dipole-dipole and hydrogen interactions because there is C-O, C=O, and O-H bonds
what can carboxylic acids form?
hydrogen bonded dimers held together by two intermolecular H-bonds
are carboxylic acids good bases or acids?
good acids: pka = 5
- conjugate base is resonance-stabilized
what is a resonance form of carboxylic acids?
carboxylate anions
what does electron withdrawing groups do to carboxylic acids?
makes it more acidic because electron withdrawing groups lower pKa by stabilizing conjugate base and reducing the electron density in the carboxylate anion
- the more groups, the more acidic
what does electron donating groups do to a carboxylic acid?
makes it more less acidic because electron donating groups destabilize the conjugate base because the electron density is being donated to a negatively charged carboxylate anion
- the more groups, the less acidic
does the distance of the electron withdrawing group effect the acidity?
yes, the closer the group is to the COOH, the more acidic
why are carboxylic acids more acidic than phenols?
because phenoxide anions only have one O atom to delocalize the negative charge
preparation of carboxylic acids
- oxidative cleavage of alkenes using KMnO4
- oxidative cleavage of alkynes
- oxidation of primary alcohols or aldehydes
oxidative cleavage of alkenes using KMnO4
reagents:
1. KMnO4, OH, heat / 2. H3O+
- breaks alkenes to make 2 carboxylic acids
oxidative cleavage of alkynes
reagent: 1. O3 / 2. H2O
breaks alkyne into 2 carboxylic acids
oxidation of primary alcohol or aldehydes
reagent: H2CrO4
- makes carboxylic acid from aldehyde or primary alcohol
oxidation of alkyl benzenes
benzene with at least one benzylic C-H bond forms a benzoic acid (benzene with carboxylic acid)
reagent: KMnO4
hydrolysis of nitriles
reagent 1: HCN
1. Br to CN
reagent 2: H+/H2O, heat
2. replaces CN with carboxylic acid
addition of CO2 to grignard reagents
reagent 1: Mg/EtO
1. adds Mg to Br
reagent 2: CO2/H3O+
2. makes MgBr into carboxylic acid
carboxylic acid derivatives
- acid chloride
- ester
- amide
nucleophilic acyl substitution
nucleophile attacks carbonyl carbon and replaces the Z
- forms tetrahedral intermediate
what cannot undergo nucleophilic acyl substitution?
ketones and aldehydes because they do not have good leaving groups
nucleophiles that can do nucleophilic acyl substitution
OH
H2O
ROH
RCOO
NH3
RNH2
R2NH
fischer esterification
treatment of carboxylic acid with an alcohol in the presence of an acid catalyst forms an ester
KNOW MECHANISM
reagent for fischer esterification
H2SO4 or strong acid
