Nucleophilic Substitiution Reactions Flashcards Preview

Advanced Higher Chemistry: Unit 2 - Organic Chemistry > Nucleophilic Substitiution Reactions > Flashcards

Flashcards in Nucleophilic Substitiution Reactions Deck (23)
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1
Q

What is the C-X bond and what does this mean?

A

it is polar and suseptible to attack by nucelophiles

2
Q

What does the nucleophile attack?

A

δ+ carbon

3
Q

Why is it called nucleophilic substitution?

A

the halgoen is replaced bu a nucleophile

4
Q

Describe the Sn1 mechanism.

A

There are 2 steps.
One species takes part in the rate determining step.
In the first step the C-X bonds breaks heterolytically to form the halide ion and a carbocation intermediate.
In the second step, a nucelophile rapidly attacks the positive carbon atom to form the product.

5
Q

Why is the Sn1 said to be first order?

A

The overall rate of reaction depends on the slow step (Rate Determining Step) which involves only one molecule

6
Q

What is the rate equation for the Sn1 mechanism?

A

Rate= k[haloalkane]

7
Q

What is the carbocation intermediate stabilised by?

A

the alkyl groups, which are electron donating i.e. they push electrons onto the positive carbon atom thereby reducing its charge and making it more stable

8
Q

What is the trend between alkyl groups and stabiliy of the carbocation?

A

The more alkyl groups there are, the more stable the carbocation

9
Q

What class of haloalkane is more likely to undergo Sn1?

A

tertiary

10
Q

Describe the Sn2 mechanism.

A

The nucleophile begins to form a bond between it and the carbom atom. At the same time, the bond between the carbon atom and the halogen starts to break.
A transition state forms in which the new bond is half-formed and the existing bond is half-broken

11
Q

What class of haloalkane is most likely to undergo Sn2 and why?

A

Primary

In order for Sn2 to occur, the carbon atom it attacks cannot be too cluttered (Sterically Hindered)

12
Q

What does the overall rate of reaction for Sn2 depend on?

A

Both reactants and, therefore, is second order

13
Q

What is the rate equation for Sn2?

A

Rate= k[haloalkane][Nu]

14
Q

What does nucleophilic substitution of haloalkanes by hydroxide ions produce?

A

alcohols

15
Q

What does a base in water favour?

A

substitution

16
Q

When are alkoxide ions formed?

A

when alcohols react with sodium metal

17
Q

What can alkoxide ions be represented with?

A

R-O-

18
Q

What are alkoxides said to be?

A

nucleophiles due to the negative charge

19
Q

What do alkoxide ions react with haloalkanes to form?

A

ethers

20
Q

What are ethers represented by?

A

R-O-R

21
Q

What do haloalkanes react with cyanide ions to form?

A

nitriles

22
Q

What does the reaction with cyanide ions do to the carbon chain?

A

increases the carbon chain length by one carbon

23
Q

What are nitriles easily hydrolysed to?

A

a carboxylic acid