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Organic Chemistry 2 Final Exam Review Cheat Sheet, Cheat Sheet of Organic Chemistry

Tufts UniversityOrganic Chemistry

Reactions, mechanisms, compounds and other data divided into 4 chapters for organic chemistry 2 course

Typology: Cheat Sheet

2020/2021

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Organic Chemistry II
Andrew Rosen
April 2, 2013
Contents
1 Aldehydes and Ketones 3
1.1 PhysicalProperties................................................... 3
1.2 SynthesisofAldehydes................................................. 3
1.2.1 ReductionandOxidation ........................................... 3
1.2.2 Mechanisms for Aldehyde Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 SynthesisofKetones.................................................. 4
1.4 SynthesisofKetoneExample ............................................. 4
1.5 Nucleophilic Addition to the Carbon-Oxygen Double Bond . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.6 The Addition of Alcohols: Hemiacetals and Acetals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.6.1 Hemiacetals................................................... 5
1.6.2 Acetals ..................................................... 6
1.6.3 CyclicAcetals.................................................. 7
1.6.4 Thioacetals ................................................... 7
1.7 The Addition of Primary and Secondary Amines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.8 The Addition of Hydrogen Cyanide: Cyanohydrins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.9 The Addition of Ylides: The Wittig Reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.10OxidationofAldehydes ................................................ 10
2 Carboxylic Acids and Their Derivatives 11
2.1 PreparationofCarboxylicAcids ........................................... 11
2.2 Acyl Substitution: Nucleophilic Addition-Elimination at the Acyl Carbon . . . . . . . . . . . . . . . . . . . . 11
2.3 AcylChlorides ..................................................... 11
2.4 CarboxylicAcidAnhydrides.............................................. 12
2.5 Esters .......................................................... 13
2.5.1 Esterication .................................................. 13
2.5.2 Saponication.................................................. 13
2.5.3 Lactones..................................................... 14
2.6 Amides ......................................................... 14
2.6.1 AmidesfromAcylChlorides.......................................... 14
2.6.2 Amides from Carboxylic Anhydrides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.6.3 AmidesfromEsters .............................................. 15
2.6.4 Amides from Carboxylic Acids and Ammonium Carboxylates . . . . . . . . . . . . . . . . . . . . . . . 15
2.6.5 HydrolysisofAmides.............................................. 15
2.6.6 Nitriles from the Dehydration of Amides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.6.7 HydrolysisofNitriles.............................................. 16
2.6.8 Lactams..................................................... 17
2.7 DerivativesofCarbonicAcid ............................................. 17
2.8 Decarboxylation of Carboxylic Acids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
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Download Organic Chemistry 2 Final Exam Review Cheat Sheet and more Cheat Sheet Organic Chemistry in PDF only on Docsity!

Organic Chemistry II

 - April 2, Andrew Rosen
  • 1 Aldehydes and Ketones Contents
    • 1.1 Physical Properties
    • 1.2 Synthesis of Aldehydes
      • 1.2.1 Reduction and Oxidation
      • 1.2.2 Mechanisms for Aldehyde Synthesis
    • 1.3 Synthesis of Ketones
    • 1.4 Synthesis of Ketone Example
    • 1.5 Nucleophilic Addition to the Carbon-Oxygen Double Bond
    • 1.6 The Addition of Alcohols: Hemiacetals and Acetals
      • 1.6.1 Hemiacetals
      • 1.6.2 Acetals
      • 1.6.3 Cyclic Acetals
      • 1.6.4 Thioacetals
    • 1.7 The Addition of Primary and Secondary Amines
    • 1.8 The Addition of Hydrogen Cyanide: Cyanohydrins
    • 1.9 The Addition of Ylides: The Wittig Reaction
    • 1.10 Oxidation of Aldehydes
  • 2 Carboxylic Acids and Their Derivatives
    • 2.1 Preparation of Carboxylic Acids
    • 2.2 Acyl Substitution: Nucleophilic Addition-Elimination at the Acyl Carbon
    • 2.3 Acyl Chlorides
    • 2.4 Carboxylic Acid Anhydrides
    • 2.5 Esters
      • 2.5.1 Esterication
      • 2.5.2 Saponication
      • 2.5.3 Lactones
    • 2.6 Amides
      • 2.6.1 Amides from Acyl Chlorides
      • 2.6.2 Amides from Carboxylic Anhydrides
      • 2.6.3 Amides from Esters
      • 2.6.4 Amides from Carboxylic Acids and Ammonium Carboxylates
      • 2.6.5 Hydrolysis of Amides
      • 2.6.6 Nitriles from the Dehydration of Amides
      • 2.6.7 Hydrolysis of Nitriles
      • 2.6.8 Lactams
    • 2.7 Derivatives of Carbonic Acid
    • 2.8 Decarboxylation of Carboxylic Acids
  • 3 Enols and Enolates
    • 3.1 Enolate Anions
    • 3.2 Keto and Enol Tautomers
    • 3.3 Reactions via Enols and Enolates
      • 3.3.1 Racemization
      • 3.3.2 Halogenation at the α Carbon
      • 3.3.3 The Haloform Reaction
    • 3.4 Lithium Enolates
    • 3.5 Enolates of β-Dicarbonyl Compounds
    • 3.6 Synthesis of Methyl Ketones: The Acetoacetic Ester Synthesis
    • 3.7 Synthesis of Substituted Acetic Acids: The Malonic Ester Synthesis
    • 3.8 Further Reactions
    • 3.9 Summary of Enolate Chemistry
  • 4 Condensation and Conjugate Addition
  • For the ester reduction, if it's a cyclic ester, the product would be an aldehyde that also has an alcohol hydroxy group (instead of the OR group being entirely replaced by H)

1.3 Synthesis of Ketones

  • The use of H 2 CrO 4 or PCC in CH 2 Cl 2 will convert a 2 ◦^ alcohol to a ketone
  • Grignard reagents or organolithium reagents can convert a nitrile to a ketone. Examples are shown below:

1.4 Synthesis of Ketone Example

  • Note that PBr 3 replaces an OH with a Br and does not have rearrangements  It is useful for creating alkyl bromides, which can then make grignard reagents
  • The creation of nitriles via this method is useful to make aldehydes using DIBAL−H

1.5 Nucleophilic Addition to the Carbon-Oxygen Double Bond

  • When the reagent is a strong nucleophile, addition takes place as follows without stereospecicity:
  • When an acid catalyst is present and the nucleophile is weak, addition takes place as follows^2 :
  • Aldehydes are more reactive than ketones in nucleophilic additions  Aldehydes have less steric hindrance at the carbonyl carbon  Aldehydes have a larger dipole moment on the carbonyl carbon

1.6 The Addition of Alcohols: Hemiacetals and Acetals

1.6.1 Hemiacetals

  • A hemiacetal is a molecule with an OH and an OR group attached to the same carbon
  • Alcohols can react with aldehydes or ketones to form hemiacetals:

(^2) The protonated carbonyl compound is called an oxonium cation and is highly reactive toward nucleophilic attack

  • An aldehyde or ketone can be converted to an acetal via acid-catalyzed formation of the hemiacetal and then acid- catalyzed elimination of water. This is followed by addition of the alcohol and loss of a proton  All steps are reversible. Be able to draw the mechanism of making an aldehyde from the acetal

1.6.3 Cyclic Acetals

  • A cylic acetal can be formed when a ketone or aldehyde is treated with excess 1,2-diol and a trace of acid (be able to write the mechanism)  This reaction can be reversed by treating the acetal with water and acid (H 3 O+)
  • Acetals are stable in basic solutions (nonreactive)
  • Acetals can act as protecting groups for aldehydes and ketones in basic solutions due to their stability  For instance, to protect a carbonyl group, one can add a cyclic acetal in HCl. Then one can perform the desired reaction without worrying about the carbonyl group. Finally, to remove the cyclic acetal and restore the carbonyl group, use H 3 O+/H 2 O

1.6.4 Thioacetals

  • An aldehyde or ketone can react with a thiol (R−SH) in HA to form a thioacetal
  • Additionally, an aldehyde or ketone can react with a di-thiol (HS−R−SH) with BF 3 to form a cyclic thioacetal
  • H 2 and Raney nickel can convert a thioacetal or cyclic thioacetal to yield hydrocarbons

1.7 The Addition of Primary and Secondary Amines

  • Imines have a carbon-nitrogen double bond
  • An aldehyde or ketone can react with a primary amine to form an imine^3

Imine Formation

  • Enamines are alkeneamines and thus have an amino group joined to a carbon-carbon double bond
  • An aldehyde or ketone can react with a secondary amine under acid catalysis to form an enamine

Enamine Formation

(^3) Note that this mechanism is dierent than what the textbook provides

  • Aldehydes and ketones react with phosphorous ylides to yield alkenes - The Wittig Reaction
  • To prepare the ylide, one can begin with a primary or secondary alykl halide

 Reacting the 1 ◦^ or 2 ◦^ alkyl halide with :P(C 6 H 5 ) 3 will cause the halide to be replaced by P+(C 6 H 5 ) 3  Using RLi will take o the hydrogen of the attached carbon of the alkane and give it a -1 charge due to the new electron pair

  • The Horner-Wadsworth-Emmons reaction is a variation of the Wittig reaction and involves the use of a phosphonate ester to make an (E)-alkene. Example shown below:
  • To prepare the phosphonate ester, (RO) 3 P can be reacted with an appropriate halide. Example shown below:

1.10 Oxidation of Aldehydes

  • The use of KMnO 4 with OH−^ or Ag 2 O with OH−^ can oxidize an aldehyde to a carboxylic acid when followed by H 3 O+

2 Carboxylic Acids and Their Derivatives

2.1 Preparation of Carboxylic Acids

  • Ozonolysis via O 3 and then H 2 O 2 workup yields carboxylic acids from alkenes
  • H 2 CrO 4 can oxidize a 1 ◦^ alcohol or aldehyde to a carboxylic acid
  • Using CO 2 and then acidication with H 3 O+^ can convert a grignard reagent to a carboxylic acid

2.2 Acyl Substitution: Nucleophilic Addition-Elimination at the Acyl Carbon

  • An acyl substitution can occur as follows but always requires a leaving group at the carbonyl carbon:
  • The order of relative reactivity of acyl compounds goes as follows: acyl chloride > acid anyhdride > ester > amide

2.3 Acyl Chlorides

  • The use of SOCl 2 , PCl 3 , or PCl 5 will yield an acyl chloride from a carboxylic acid:

2.5 Esters

2.5.1 Esterication

  • Carboxylic acids react with alcohols to form esters through esterication

 Fischer esterications are acid-catalyzed

  • An acyl chloride can be reacted with an alcohol in pyridine to form an ester
  • Carboxylic acid anhydrides react with alcohols to form esters in the absence of an acid catalyst
  • Cyclic anhydrides react with an alcohol to form compounds that are both esters and carboxylic acids

2.5.2 Saponication

  • One can reux an ester with a strong base such as NaOH in water to produce an alcohol and carboxylate salt

2.5.3 Lactones

  • Carboxylic acids with a γ or δ (3rd or 4th adjacent) carbon can undergo intramolecular esterication to form cyclic esters - lactones
  • The forward reaction is:
  • The reverse process is:

2.6 Amides

2.6.1 Amides from Acyl Chlorides

  • A 1 ◦^ amine, 2 ◦^ amine, or ammonia can react with an acyl chloride to form an amide

2.6.2 Amides from Carboxylic Anhydrides

  • A 1 ◦^ amine, 2 ◦^ amine, or ammonia can react with an acid anhydride to form an amide
  • Amides hydrolyze under heated aqueous base to form a carboxylate anion

2.6.6 Nitriles from the Dehydration of Amides

  • Amides react with P 4 O 10 or (CH 3 CO 2 )O to form nitriles

2.6.7 Hydrolysis of Nitriles

  • Nitrile hyrdolysis yields a carboxylic acid or carboxylate anion
  • The mechanisms are shown below:

2.6.8 Lactams

  • γ and δ amino acids spontaneously form γ and δ cyclic amides - lactams

2.7 Derivatives of Carbonic Acid

  • Reacting a carbonyl dichloride with an alcohol leads to an alkyl chloroformate

 These alkyl chloroformates can react with ammonia or amines to form carbamates (urethanes)

  • Benzyl chloroformate can be used to create a protecting group, and it can be removed by H 2 /Pd-C or HBr in CH 3 CO 2 H
  • Diastereomers that dier in conguration at only one of multiple chirality centers are known as epimers

3.3.2 Halogenation at the α Carbon

  • Carbonyl compounds that have an α hydrogen can undergo halogen substitution at the α carbon in acid or base

3.3.3 The Haloform Reaction

  • Multiple halogenations occur when methyl ketones react with halogens in excess base
  • The haloform reaction converts methyl ketones to carboxylic acids

3.4 Lithium Enolates

  • A strong base like LDA can convert a carbonyl compound to an enolate
  • The more highly substituted enolate is the more stable one and predominates under conditions where interconversion may occur

 Use of hydroxide or an alkoxide will form this  This enolate is known as the thermodynamic enolate

  • The enolate formed from removal of the least sterically hindered α hydrogen forms under conditions that do not favor equilibrium among possible enolates

 Use of LDA in THF or DME will form this  This enolate is known as the kinetic enolate

  • Enolates can be alkylated when a primary alkyl halide is used:
  • Esters can be directly alkylated using LDA in THF or DME and then a primary halide:

3.5 Enolates of β-Dicarbonyl Compounds

  • An RO−^ base can form an enolate from a β-dicarbonyl compound

3.6 Synthesis of Methyl Ketones: The Acetoacetic Ester Synthesis

  • An example of acetoacetic ester synthesis is shown below,