Reactions And Mechanisms 1 Flashcards

1
Q

Name the functional groups only containing σ bonds

A

Alcohols
Ethers
Amines
Halides

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2
Q

Functional groups containing π bonds

A
Alkenes
Alkynes
Aldehydes
Ketones
Carboxylic acids
Esters
Acid halides
Anhydrides
Amides
Nitriles
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3
Q

What are the primary considerations for molecular interactions?

A

HOMO/LUMO interactions

Electrostatic interactions

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4
Q

The best bonding interaction is between which two things?

A

HOMO of the nucleophile

LUMO of the electrophile

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5
Q

What do curly arrows represent?

A

Movement of a pair of electrons from a filled orbital (HOMO) to an empty orbital (LUMO)

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6
Q

Order the nucleophile types in order of nucleophilicity

A

-ve charge > lone pair > π bond > σ bond

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7
Q

Order the electrophile types in order of electrophilicity

A

Empty orbital > π* orbital > σ* orbital

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8
Q

Where is the strongest interaction with a nucleophile and a carbonyl?

A

π* on the C

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9
Q

What is the best source of hydride for reducing an aldehyde or a ketone?

A

Sodium borohydride

NaBH4

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10
Q

What are the two types of organometallic reagents?

A

R-Li

R-MgBr

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11
Q

How are the organometallic reagents synthesised?

A

R-X -(Mg, Ether)-> R-MgBr

R-X -(2Li, Ether)-> R-Li + Li-X

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12
Q

What is the third way to synthesise an alkynyl organometallic reagent?

A

Use a strong nitrogen base
Such as NaNH2
NaNH2 made from reacting Na + NH3

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13
Q

What are the two reaction steps for reacting an organometallic reagent with an aldehyde/ketone?

A
  1. R-MgBr

2. H2O

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14
Q

Why must organometallic reagent reactions be done in two steps?

A

They are incompatible with water

Water destroys the organometallic by protonating the carbanion

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15
Q

How are hydrates formed?

A

Reacting water with aldehydes or ketones

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16
Q

How are hemiacetals and acetals formed?

A

Reacting alcohols with aldehydes or ketones

17
Q

Why is it easier to form hydrates from aldehydes over ketones?

A

As the bond angle is reduced from 120 to 109.5

Harder to form hydrate with ketones as steric clash is increased in the product

18
Q

Acid and base catalysts can be used in both hydrate and hemiacetal formation, what do the do?

A

Acid: make the carbonyl more electrophilic by protonation
Base: make the nucleophile more nucleophilic (deprotonation)

19
Q

Why can acetals only be formed using acid catalysis?

A

An OH group must be made into a good leaving group

That can’t happen in basic conditions

20
Q

What is one way to determine which leaving group is best?

A

Consider the acidity of the conjugate acids formed from the anions upon leaving
Strongest acid makes for the best leaving group

21
Q

Why do organometallic reactions generate a tetrahedral product and not a trigonal product?

A

None of the leaving groups are good