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Organic Chemistry > Chapter 19: Aldehydes and Ketones > Flashcards

Chapter 19: Aldehydes and Ketones Flashcards

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1
Q

Naming an aldehyde

A
  1. Identify and name the parent chain that includes the aldehyde group
  2. Identify and name substituents
  3. Assign locant to each substituent giving the aldehyde the lowest number
  4. Assemble substituents alphabetically
  5. Assign configurations to any chiral centers
  6. Replace “e” with suffix −al
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2
Q
A

Cyclohexanecarbaldehyde

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3
Q
A

Formaldehyde

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4
Q
A

Acetaldehyde

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5
Q
A

Benzaldehyde

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6
Q

Naming ketones

A
  1. Identify and name the parent chain that includes the ketone carbonyl
  2. Identify and name substituents
  3. Assign locant to each substituent giving the ketone the lowest number
  4. Assemble substituents alphabetically
  5. Assign configurations to any chiral centers
  6. Replace “e” with suffix −one
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7
Q

Naming simple ketones

A

Simple ketones can be named alkyl alkyl ketones

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8
Q
A

Acetone

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9
Q
A

Acetophenone

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10
Q
A

Benzophenone

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11
Q

Preparing aldehydes from primary alcohols

A

Reagents

PCC & CH2Cl2 (dichloromethane)

or

Des-Martin periodinane (DMP) oxidation
DMP and CH2Cl2 (dichloromethane)

or

Swern oxidation
1. DMSO & (COCl)2 (oxalyl chloride)
2. Et3N (triethylamine)

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12
Q

Preparing ketones from secondary alcohols

A

Reagents

Na2Cr2O7 (sodium dichromate) & H2SO4/H2O

or

xs CrO3 (chromium trioxide) & H3O+/acetone

or

PCC & CH2Cl2 (dichloromethane)

or

Des-Martin periodinane (DMP) oxidation
DMP & CH2Cl2 (dichloromethane)

or

Swern oxidation
1. DMSO & (COCl)2 (oxalyl chloride)
2. Et3N (triethylamine)

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13
Q

Preparing aldehydes or ketones from an alkene

A

Depending on the substitution of the alkene either can be created

Reagents

  1. O3
  2. DMS
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14
Q

Forming an aldehyde from a terminal alkyne

A

Hydroboration oxidation

Reagents

  1. R2BH (alkyl borane)
    Disiamylborane or 9-BBN
  2. H2O2 & NaOH
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15
Q

Forming an acetyl ketone from an alkyne

A

Acid-catalyzed hydration

Reagents

H2SO4, H2O & HgSO4 (mercuric sulfate)

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16
Q

Aldehyde vs. ketone reactivity

A
17
Q

Formation of hydrates

A

Reagents

[H+] & ROH

Alcohols can attack carbonyls making acetals

Ketal- specifically from a ketone

  • For most ketones, the ketal is NOT favored at equilibrium

Acetal- typically from an aldehyde

  • For simple aldehydes the acetal is favored at equilibrium
18
Q

Cyclic acetal formation

A

Reagents

[H+], ethylene glycol

Typically, a non-nucleophilic acid is used like H2SO4

Can be used as a protecting group as it is reversible

19
Q

Hemiacetal formation

A

An acetal with one −OR group and one hydroxyl group

Difficult to isolate however cyclic hemiacetals can be isolated

20
Q

Imine formation

A

Reagents

[H+] & RNH2

Mechanism

Under acidic conditions aldehydes/ketones react with primary amines to form imines

21
Q

Formation of an enamines

A

Reagents

[H+] & R2NH

Mechanism

Under acidic conditions aldehydes/ketones react with secondary amines to form enamines

22
Q

Wolff-Kishner Reduction

A

Reagents

  1. [H+] & H2N−NH2 (hydrazine)
  2. KOH, H2O & heat

Mechansim

Reduce a carbonyl to alkane

23
Q

Hydrolysis of acetals

A

Reagents

[H+] & H2O

Mechanism

Acetals are hydrolyzed with aqueous acid to yield a ketone (or aldehyde) and two equivalents of alcohol

Simply the reverse of acetal formation

24
Q

Hydrolysis of imines and enamines

A

Reagents

[H+] & H2O

Mechanism

Acetals are hydrolyzed with aqueous acid to yield a ketone (or aldehyde) and a primary or secondary amine

25
Q

Thioacetal formation

A

Reagents

[H+] & RSH

Mechanism

Nucleophilic attack similar to alcohols

26
Q

Cyclic thioacetal formation

A

Reagents

[H+], 1,2-ethanedithiol

27
Q

Reduction of thioacetals

A

Reagents

Raney Ni

28
Q

Hydrogen nucleophiles

A

Reagents

  1. LiAlH4
  2. H2O

or

NaBH4, MeOH

Mechanism

Can act as reducing agents by delivering hydrides

Need basic conditions because hydrides are strong nucleophiles

29
Q

Gringard reagents

A

Reagents

  1. RMgX
  2. H3O+

Mechanism

A Grignard reagent is formed by the reaction between an alkyl halide and magnesium characterized by a C−Mg bond; acts as a nucleophile and attacks a carbonyl carbon

CANNOT be used in the presence of a mildy acidic proton as it will just deprotonate the substrate; NOT compatible with carboxylic acids

Regeoselectivity

Attaches the R group to the carbonyl carbon; subsequent workup protonates the carbonyl oxygen creating a hydroxyl group

Stereospecificity

Nuclephilic attack can occur form either side; forms a mixture of enantiomers when a chiral center is present

30
Q

Cyanohydrin formation

A

Reagents

KCN & HCN

or

KCN & HCl

Mechanism

Produces a mixture of enantiomers if a new chiral center is formed

31
Q

Wittig reaction

A

Reagents

Whittig reagent
R=PPh3 (phosphorous ylide)

Mechanism

Converts a ketone or aldehyde into an alkene by forming a new C=C

Inserts the R group on the ylide at the location where the carbonyl oxygen was

When the Whittig reagent is generated from a simple alkyl halide the (Z)-alkene is generally the major product

When the Whittig reagent contains an electron-withdrawing group the (E)-alkene is generally the major product

32
Q

Whittig reagent preparation

A

Reagens

  1. PPh3 (triphenylphosphine)
  2. Strong base
    n-BuLi. NaH, NaNH2, or PhLi

Mechanism

Retrosynthetic analysis reveals two possibly ways to make product. Which is better?

Look at which Wittig reagent is easier to make, methyl halide is better

33
Q

Baeyer-Villiger oxidation

A

Reagents

RCO3H (peroxy acid)

Mechanism

Inserts an oxygen between a carbonyl carbon and an alkyl group

  • Converting an aldehyde to a carboxylic acid
  • Converts a ketone to an ester

For an aldehyde or unsymmetrical ketone the rate of migration is H > 3° > 2°, Ph > 1° > methyl

Organic Chemistry (18 decks)

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