major concepts of organic chemistry lecture

7/30/2019 Major Concepts of Organic Chemistry lecture

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Things I GetConfused OverAll through the course


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Isomers

Isomers

Constitutional

Bonded differently

ConfigurationalBonded the same;

different in space

Conformational

Bond can be rotatedaround single bond to

get the isomers the same

E/Z isomers

(alkenes)

Stereoisomers

Need to break bond to be thesame

Cis/Trans

EnantiomersNon-superimposable mirror

images of each other

DiastereomersNot mirror images of

each other


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Mechanisms

Addition

Substitution

Nucleophilic addition(Halide Reduction)

Uses LiAlH4orNaBH4as

reagent

aldehydes = 1 alcohol

ketone = 2 alcohol

AromaticElectrophilicsubstitution

Electrophilic additionAll for alkene reactions

Hydrogenation uses Pd/C

catalyst to break H2

Halogenation

Hydrohalogenation

Hydration- uses dilute H2SO4

Nucleophilicacyl substitution

Uses SOCl2asreagent

Nucleophilicsubstitution

For haloalkanes

e.g. SN1 and SN2

OxidationUses Cr2O7

2/H+ to add oxygen

1 alcohol and aldehyde =

carboxylic acid

2 alcohol = ketone

Elimination

Dehydration of alcohols(elimination of water)

Uses conc H2SO4Lecture 9

DehydrohalogenationElimination of the halogenin haloalkanes to formalkenes

e.g. E1 and E2Uses conc. KOHe,.g. grignard reactionUses MgBr as reagent


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Addition Reactions Electrophilic addition

Nucleophilic addition

Grignard reactions

Halide reduction

Hydration

Halogenation

Hydrohalogenation

Hydrogenation


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Electrophilic addition

Dilute

Lots of alkenesundergo

electrophilicreactions.

Electron richdouble bondattacks electron

deficient things.


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Nucleophilic addition

Undergone by aldehydes 1 and ketones2 to get back alcohols.

3 important examples of nucleophilicaddition.

Grignard reaction: C- via R-MgBr reagent.

Halide Reduction: H- via LiAlH4 or NaBH4

Grignard reaction: R-MgBr reagent with

CO2 to form carboxylic acid.


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Examples using carboanion


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Examples via hydride ion


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While on the topic ofketones and alcohols . . .Oxidation


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Oxidation

Reverse reaction for aldehydes andketones.

Use to make carboxylic acids andketones


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Oxidation


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Examples


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Elimination Reactions E1

E2 Dehydration


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Elimination of haloalkanes The removal of the halogen in halkoalkanes is

facilitated by hot, conc. KOH reagent.

This results in the formation of an alkene. Recall Zaitsevs rule that the major product is the

most substituted alkene.

Two elimination reactions: E1

E2

In SN2reactions, the carbocation formed caneither go through elimination or continue on withthe second step of nucleophilic substitution.


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E1

Again, like SN2 steric hindrance alsoapplies in E2 and those which have a lot

of groups around the carbon will undergoE1 instead.

Due to the carbocation, the environmentis polar.


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E2

The reaction is dependent on theconcentration of the base and on the

concentration of the reagent.

No charged species so the environment isnon polar.


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Dehydration

Works for alcohols to form alkenes.


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Grignard Reagents

Halogens are nucleophiles. Therefore theywill be attracted to


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List of all the Reactions

Reaction ReagentOxidation Cr2O7

2-

Reduction NaBH4/ LiAlH4

Hydrogenation H2/Pd (C)

Dehydration Conc. H2SO4

Hydration Dilute H2SO4

Halogenation Br2, F2, I2

Hydrohalogenation HBr, HF, HI

Nucleophilic substitution nucleophile

Grignard reactions Mg2+ usually as MgBr, MgI

Elimination Hot, conc. KOH

Nucleophilic aromatic substitution

Nucleophilic acyl substitution SOCl2

Hydrolysis H2O


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Nucleophilic Substitution

Nucleophilic substitution includes


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Reminders

Is there a double bond?- is the reagent anelectrophile?

major concepts of organic chemistry lecture

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