Organic ChemistryProblem Solving Approach

• Reactions• Synthesis• Distinguishing• Elucidation

Organic Chemistry

There are generally 4 types of questions in Organic Chemistry:

Problem Solving Approach

1. Given reactants + products suggest reagents and conditions

2. Given reactants + reagents suggest products

3. Given new reaction (Grignard, Killiani-Fishcer, Azo, Wittig) suggest products

4. Given reactants/ products/ reagents state type of reaction

ReactionsThere are generally 4 types of questions for ‘Reaction’ qns:

Problem Solving Approach

1. Given reactants + products suggest reagents and conditions

Strategy:memorise, memorise and memorise

ReactionsProblem Solving Approach

2. Given reactants + reagents suggest products

Strategy:Identify ALL FG in reactantsReact ALL with reagentsBe careful of Markonikov, Saytseff etc.

ReactionsProblem Solving Approach

2. Given reactants + reagents suggest products

Strategy:Clarify minor differences e.g.Can NaBH4 reduce carboxylic acids? No

Can K2Cr2O7 cleave C=C? No

Can H2/ Pt reduce nitrobenzene? Yes

ReactionsProblem Solving Approach

3. Given new reaction (Grignard, Killiani-Fishcer, Azo, Wittig) suggest products

Strategy:Identify pattern of reactionApply pattern/ rule to new reactant

ReactionsProblem Solving Approach

4. Given reactants/ products/ reagents state type of reaction

Strategy:Identify FG that undergoes reactionRecall what types of reaction that FG can undergo.Note:Halogenation, hydrogenation, hydration etc are not types of reactions

ReactionsProblem Solving Approach

Strategy1. Count no. of C in reactant & product+1 Add CN–

–1 Iodoform or Oxidative cleavage 2. Work backwards from product until stuck.What compound can be used to form this product? 3. Work forward from reactant.What reactions can this compound undergo?

SynthesisProblem Solving Approach

Strategy

- Spot the difference (FG or structure)

FG: Use a test specific to the FG present in only one of the two compounds.

Structure: Most of the time Iodoform or selective oxidation

DistinguishingProblem Solving Approach

Note:

In general, there is no FG test for esters and amides. They need to be hydrolysed into their respective acid/alcohol/amine before testing.

Exception: 1⁰ amides produce NH3 on hydrolysis

DistinguishingProblem Solving Approach

Strategy

1. Make as many deductions as possible from the information given in the question.

2. Start identifying from the unknown with the most information/ deductions.

3. Make sure all reactions/ observations are accounted for in your answer.

ElucidationProblem Solving Approach