Aldehydes and ketones nucleophilic addition to the carbonyl group
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Aldehydes and Ketones Nucleophilic Addition to the Carbonyl Group. ALDEHYDES AND KETONES “carbonyl” functional group: Aldehydes Ketones. O. O. H. H. O. O. HCCHCH. IUPAC Nomenclature of Aldehydes. 4,4-dimethylpent an al. 5-hex en al or hex-5-en al.

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Aldehydes and Ketones Nucleophilic Addition to the Carbonyl Group

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Aldehydes and KetonesNucleophilic Additionto theCarbonyl Group


ALDEHYDES AND KETONES

“carbonyl” functional group:

Aldehydes Ketones


O

O

H

H

O

O

HCCHCH

IUPAC Nomenclature of Aldehydes

4,4-dimethylpentanal

5-hexenal

or hex-5-enal

2-phenylpropanedial(keep the -e endingbefore -dial)


O

O

CH3CH2CCH2CH2CH3

CH3CHCH2CCH3

CH3

H3C

O

Substitutive IUPAC Nomenclature of Ketones

Base the name on the chain that contains the carbonyl group and replace -e with -one. Number the chain in the direction that gives the lowest number to the carbonyl carbon.


O

O

CH3CH2CCH2CH2CH3

CH3CHCH2CCH3

CH3

H3C

O

Substitutive IUPAC Nomenclature of Ketones

3-hexanone

or Hexan-3-one

4-methyl-2-pentanone

or 4-methylpentan-2-one

4-methylcyclohexanone


Special names!


ALDEHYDES AND KETONES

“carbonyl” functional group:

Aldehydes Ketones


Aldehydes, IUPAC nomenclature:

Parent chain = longest continuous carbon chain containing the carbonyl group; alkane, drop –e, add –al. (note: no locant, -CH=O is carbon #1.)

CH3

CH3CH2CH2CH=O CH3CHCH=O

butanal 2-methylpropanal

H2C=OCH3CH=O

methanalethanal


Physical properties:

polar, no hydrogen bonding

mp/bp are relatively moderate for covalent substances

water insoluble

(except: four-carbons or less)


  • Reactions of aldehydes and ketones:

  • oxidation

  • reduction

  • nucleophilic addition

  • Aldehydes are easily oxidized, ketones are not.

  • Aldehydes are more reactive in nucleophilic additions than ketones.


alkane

alcohol

reduction

reduction

aldehyde

ketone

addition

product

nucleophilic

addition

oxidation

carboxylic acid


nucleophilic addition to carbonyl:


  • 1) Oxidation

  • Aldehydes(very easily oxidized!)

  • CH3CH2CH2CH=O + KMnO4, etc.  CH3CH2CH2COOH

  • carboxylic acid

  • CH3CH2CH2CH=O + Ag+ CH3CH2CH2COO- + Ag

  • Tollen’s test for easily oxidized compounds like aldehydes.

  • (AgNO3, NH4OH(aq))

Silver mirror


  • 2) Reduction:

  • To alcohols


5) Addition of alcohols


“The Grignard Song” (sung to the tune of “America the Beautiful”)

Harry Wasserman

The carbonyl is polarized,

the carbon end is plus.

A nucleophile will thus attack

the carbon nucleus.

The Grignard yields an alcohol

of types there are but three.

It makes a bond that corresponds

from “C” to shining “C.”


Dehydration of an alcohol?

CH3 H+

CH3CHCHCH3 yields a mixture of alkenes

OH

CH3 H+

CH3CHCH2CH2-OH yields a mixture of alkenes

E1 mechanism via carbocation!


Carboxylic acids:

R-COOH, R-CO2H,

Common names:

HCO2Hformic acidL. formica ant

CH3CO2Hacetic acidL. acetum vinegar

CH3CH2CO2Hpropionic acidG. “first salt”

CH3CH2CH2CO2Hbutyric acidL. butyrum butter

CH3CH2CH2CH2CO2Hvaleric acidL. valerans


5 4 3 2 1

C—C—C—C—C=O

δ γ β αused in common names


special names


IUPAC nomenclature for carboxylic acids:

parent chain = longest, continuous carbon chain that contains the carboxyl group  alkane, drop –e, add –oic acid

HCOOHmethanoic acid

CH3CO2Hethanoic acid

CH3CH2CO2Hpropanoic acid

CH3

CH3CHCOOH2-methylpropanoic acid

Br

CH3CH2CHCO2H2-bromobutanoic acid


dicarboxylic acids:

HOOC-COOHoxalic acid

HO2C-CH2-CO2Hmalonic acid

HO2C-CH2CH2-CO2Hsuccinic acid

HO2C-CH2CH2CH2-CO2Hglutaric acid

HOOC-(CH2)4-COOHadipic acid

HOOC-(CH2)5-COOHpimelic acid

Oh, my! Such good apple pie!


salts of carboxylic acids:

name of cation + name of acid: drop –ic acid, add –ate

CH3CO2Nasodium acetate or sodium ethanoate

CH3CH2CH2CO2NH4 ammonium butyrate

ammonium butanoate

(CH3CH2COO)2Mg magnesium propionate

magnesium propanoate


physical properties:

polar + hydrogen bond  relatively high mp/bp

water insoluble

exceptions: four carbons or less

acidic turn blue litmus  red

soluble in 5% NaOH

RCO2H + NaOH  RCO2-Na+ + H2O

stronger stronger weaker weaker

acid base base acid


  • RCO2HRCO2-

  • covalentionic

  • water insolublewater soluble

  • Carboxylic acids are insoluble in water, but soluble in 5% NaOH.

  • Identification.

  • Separation of carboxylic acids from basic/neutral organic compounds.

  • The carboxylic acid can be extracted with aq. NaOH and then regenerated by the addition of strong acid.


  • Carboxylic acids, syntheses:

  • oxidation of primary alcohols

  • RCH2OH + K2Cr2O7 RCOOH

  • 2.oxidation of arenes

  • ArR + KMnO4, heat  ArCOOH


  • oxidation of 1o alcohols:

  • CH3CH2CH2CH2-OH + CrO3 CH3CH2CH2CO2H

  • n-butyl alcohol butyric acid

  • 1-butanol butanoic acid

  • CH3 CH3

  • CH3CHCH2-OH + KMnO4  CH3CHCOOH

  • isobutyl alcohol isobutyric acid

  • 2-methyl-1-propanol` 2-methylpropanoic acid


  • oxidation of arenes: Remember for Benzaldehyde!!

note: aromatic acids only!


  • carboxylic acids, reactions:

  • as acids

  • conversion into functional derivatives

  • a)  acid chlorides (Never Mind! But use SOCl2 if needed)

  • b)  esters (use an alcohol and name!)

  • c)  amides (following chapter, 16!)


  • as acids:

  • with active metals

  • RCO2H + Na  RCO2-Na+ + H2(g)

  • with bases

  • RCO2H + NaOH  RCO2-Na+ + H2O

  • relative acid strength?

  • CH4 < NH3 < HCCH < ROH < HOH < H2CO3 < RCO2H < HF


Resonance stabilization of the carboxylate ion decreases the ΔH, shifts the ionization in water to the right, increases the Ka, and results in carboxylic acids being stronger acids.


  •  esters

  • “direct” esterification: H+

  • RCOOH + R´OH  RCO2R´ + H2O

  • -reversible and often does not favor the ester

  • -use an excess of the alcohol or acid to shift equilibrium

  • -or remove the products to shift equilibrium to completion

  • “indirect” esterification:

  • RCOOH + PCl3 RCOCl + R´OH  RCO2R´

  • -convert the acid into the acid chloride first; not reversible


  •  amides

  • “indirect” only!

  • RCOOH + SOCl2 RCOCl + NH3  RCONH2

  • amide

  • Directly reacting ammonia with a carboxylic acid results in an ammonium salt:

  • RCOOH + NH3 RCOO-NH4+

  • acid base


  • Reduction:

  • RCO2H + LiAlH4; then H+ RCH2OH

  • 1o alcohol

  • Carboxylic acids resist catalytic reduction under normal conditions.

  • RCOOH + H2, Ni  NR


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