Organic Chemistry Chapter 19

aldehyde

ketone

naming aldehydes ending & numbering

-e becomes -al

C=O carbon is always numbered 1

naming ketones ending & numbering

-e becomes -one

C=O carbon given lowest number (doesn’t have to be 1)

formaldehyde

acetaldehyde

benzaldehyde

acetone

acetophenone

benzophenone

name for aldehyde next to a ring

carbaldehyde

(entire molecule is cyclo___carbaldehyde)

3 methods of preparing aldehydes

oxidation

ozonolysis

hydroboration-oxidation of terminal alkenes

preparing aldehydes oxidation what it looks like

preparing aldehydes oxidation reagents

PCC, CH2Cl2

OR

DMP, CH2Cl2

OR

1)DMSO, (COCl)2

2) Et3N

preparing aldehydes ozonolysis what it looks like

preparing aldehydes ozonolysis reagents

1)O3

2)DMS

preparing aldehydes hydroboration-oxidation what it looks like

preparing aldehydes hydroboration-oxidation reagents

1) R2BH

2) H2O2, NaOH

4 methods of preparing ketones

oxidation of secondary alcohols

ozonolysis

acid-catalyzed hydration

friedel-crafts acylation

preparing ketones oxidation of secondary alcohols what it looks like

preparing ketones oxidation of secondary alcohols reagents

Na2Cr2O7

H2SO4, H2O

preparing ketones ozonolysis what it looks like

preparing ketones ozonolysis reagents

1) O3

2) DMS

preparing ketones acid-catalyzed hydration what it looks like

preparing ketones acid-catalyzed hydration reagents

H2SO4, H2O

HgSO4

preparing ketones friedel-crafts acylation what it looks like

preparing ketones friedel-crafts acylation reagents

ClCOR (carbonyl w Cl & R coming off)

AlCl3

what allows nucleophilic addition reaction to occur on aldehydes/ketones

carbonyl carbon is electrophilic due to resonance and induction so can be attacked by nucleophiles

are aldehydes or ketones more reactive for nucleophilic addition reactions and why

aldehydes - less sterically hindered and larger partial positive charge on carbonyl (less stabilized)

nucleophilic addition reactions with strong nucleophiles conditions

basic

nucleophilic addition reactions basic conditions mechanism

nucleophilic addition reactions with weak nucleophiles conditions

acidic

nucleophilic addition reactions acidic conditions mechanism

nuc addition to C=O equilibrium favors reactants when

nucleophile can function as a good leaving group

nuc addition to C=O equilibrium favors products when

nucleophile is a bad leaving group

ketone/aldehyde hydrate looks like

speed of ketone/aldehyde to hydrate reaction

slow unless using acidic or basic conditions

when is hydrate vs. reactants favored at equilibrium

hydrate is favored only with simple aldehydes as reagent, otherwise reactants are favored

hydrate formation under basic conditions mechanism

hydrate formation under acidic conditions mechanism (I put in the reverse reaction for some reason so pretend it’s flipped)

reagents for ketone/aldehyde to form hydrate

ketone/aldehyde & H2O

acetal/ketal what it looks like

reagents for aldehyde-acetal/ketone-ketal

aldehyde/ketone and 2 alcohols

commonly used acid catalysts for acetal/ketal formation

TsOH (p-toluenesulfonic acid)

sulfuric acid

mechanism of acetal formation (acidic conditions)

acetal formation if a diol is used instead of 2 separate alcohol molecules

forms cyclic acetal

benefit of forming cyclic acetals

can usually isolate cyclic hemiacetal but not regular hemiacetal

reagents to convert acetal back to aldehyde/ketone

H2O, H+

how to favor acetal formation from aldehyde/ketone

remove H2O

common acetal synthesis use

as protecting group

acetal as protecting group example

usually would use LAH (LiAlH4) to remove carbonyl from ring, but this would also remove the ketone, which we don’t want. If an acetal is formed first, LAH can be used to remove the carbonyl, and then add H3O+ to get desired product.

reagents to form imine

ald/ket, primary amine, acidic conditions

[H+], CH3NH2, -H2O

formation of imine what it looks like

imine formation mechanism

hydrazones

imine analogs from hydrazines, middling stability

oximes

imine analogs from hydroxylamines, most stable

reagents for enamine formation

ald/ket, secondary amine, acidic conditions

enamine formation mechanism

what is wolff-kirschner reduction what it does & its steps

2 step synthesis to reduce ketone to alkane

1) form hydrazine

2) elimination

reagents for wolff-kirscher reduction

first reduction: H+, NH2-NH2, subtract H2O

second reduction: KOH/H2O, heat

wolff-kirscher reduction what it looks like

wolff-kirschner mechanism

hydrolysis of acetals what it does

acetal and aqueous acid is reduced to a ketone/aldehyde and 2 eqs of alcohol (is the reverse of acetal formation)

hydrolysis of acetals what it looks like

conditions required for acetal hydrolysis

acidic (no reaction will occur under basic conditions!)

acetal hydrolysis mechanism

imine & enamine hydrolysis what it looks like

hydrolysis reagents

acetal/imine/enamine & H2O, +H

imine & enamine hydrolysis mechanism

reverse of their formation, similar to acetal hydrolysis (didn’t draw in class)

3 methods of reducing ketone/aldehyde to alkane

• using raney nickel

• wolff-kirschner reduction

• clemmenson reduction

clemmenson reduction (ch 18 review) and conditions/limitations

get rid of carbonyl

uses Zn(Hg) & H2O

takes place in strong acidic conditions

can’t use with cmps sensitive to acid

wolff-kirscher reduction conditions/limitations

needs strong basic conditions

sensitive to bases

can’t use with cmps

ketone/aldehyde to alkane reduction w raney nickel what it looks like

reaction of ket/ald with thiol what it looks like

reagents for ket/ald thiol rxn

H+, ket/ald reacts with 2RSH to make thioacetal, reacts with SH(CH2)2SH to make cyclic thioacetal

reagent for cyclic thioacetal to alkane

raney nickel

reagents for ket/ald to alkane w raney nickel

1) H+, HS(CH2)2SH

2) raney nickel

ket/ald to alkane w raney nickel limitations

difficult lab workup

reagents for ald/ket to alcohol

hydride reagent:

1) LiAlH4

2) H2O

OR

NaBH4, MeOH

reduction of asymmetrical ket to alcohol forms…

new chiral center

ket/ald to alcohol mechanism