Nucleophilic substitution

What do Halogenoalkanes contain?

Polar bond

1 of 22

What is electronegativity? Why?

Measure of ability/tendency of an atom to attract a bonding pair of electrons in a covalent bond. Covalent bonds share electrons but not equally

2 of 22

What is bond enthalpy more important than in?

Bond polarity in determining reactivity

3 of 22

What is the most reactive? What does it do? What has strongest/ weakest bond?

The weakest bond. Influence rate of reaction. Carbon-Fluorine stronger, Carbon-Iodine weaker

4 of 22

What does boiling point increase with? Trends?

Increased chain length. Increases going down group

5 of 22

What makes a bond polar?

Electronegativity of an atom

6 of 22

Why is the C-X bond always polar (X= halogen)?

Halogens are more electronegative than carbon (slightly positive C)

7 of 22

Why do Haloalkanes have HIGHER boiling points than HYDROCARBON chains of similar lengths?

Greater relative molecular mass and polarity

8 of 22

Why does the carbon-halogen bond enthalpy influence the rate of reaction?

The carbon-halogen bond has to be broken during the reaction. The harder the bond is to break (the higher the bond enthalpy) the slower the haloalkanes react.

9 of 22

What is a Nucleophile?

Electron pair (lone pair) donor

10 of 22

What is nucleophilic substitution undergone in?

Haloalkane

11 of 22

Examples of 3 nucleophiles?

OH-,CN- and NH3

12 of 22

WHERE DO YOU DRAW THE ARROW FROM!

THE LONE PAIR OF ELECTRONS!!!

13 of 22

Describe what happens in Nucleophillic Sub with hydroxide ions and Bromoethane

The OH- nucleophile attacks the slightly positive Carbon atom that was bonded to the halogen. This then bonds to the ethane forming ethanol and a Bromide Ion

14 of 22

Give overall equation for Hydroxide ion and Bromoethane

CH3CH2Br + OH- = CH3CH2OH+Br-

15 of 22

Describe what happens with the nucleophilic sub with Cyanide ions and bromoethane

CN- nucleophile attacks slightly positive carbon atom that was bonded to the halogen. This then bonds to the carbon removing the Br forming propanenitrile and a Br- ion

16 of 22

Give eqn for reaction of cyanide with bromoethane

CH3CH2Br+CN-=CH3CH2CN+ Br-

17 of 22

Describe what happens with the nucleophilic substitution of Ammonia with bromoethane

NH3 attacks the slightly positive carbon atom bonded to the halogen and bonds with the carbon forming Br- and CH3CH2NH2-H. The nitrogen now has a positive charge as can only bond to 2 atoms and is now bonded to 3

18 of 22

What next?

so the H donates both electrons to the NH2 and another NH3 bonds to the hydrogen

19 of 22

Eqn for it

CH3CH2Br+2NH3=CH3CH2NH2+NH4+Br-

20 of 22

What does the rate of nucleophilic substitution depend on?

Strength of carbon halogen bond rather than degree of polarisation in bond

21 of 22

Which bond is weakest? so?

C-I so most readily undergo's substitution so ror highest

22 of 22

Get Revising

Nucleophilic substitution

Other cards in this set

Card 2

Front

Back

Card 3

Front

Back

Card 4

Front

Back

Card 5

Front

Back

Comments

Similar Chemistry resources:

Other cards in this set

Card 2

Front

Back

Card 3

Front

Back

Card 4

Front

Back

Card 5

Front

Back

Comments

Related discussions on The Student Room

Similar Chemistry resources: