organic mechanisms (add benzene stuff)

Question 1

heterolytic fission is represented by what notation

Answer 1

a full arrow

Question 2

what is heterolytic fission

Answer 2

the movement of a covalent bonding pair of electrons to the same atom to break the bond.

Question 3

homolytic fission is represented by what notation

Answer 3

a partial arrow

Question 4

what is homolytic fission

Answer 4

the movement of a covalent bonding pair of electrons to different atoms to break the bond.

Question 5

what is an electrophile

Answer 5

a species that is attracted to negative charge, therefore receives a pair of electrons.

Question 6

what is a nucleophile

Answer 6

a species that is attracted to positive charge, therefore donates a pair of electrons

Question 7

what mechanism does Br2 or HBr react with alkenes by

Answer 7

electrophilic addition (only learn these two)

Question 8

what mechanism does NaOH react with haloalkanes by

Answer 8

nucleophilic substitution

Question 9

what mechanism do carbonyls react with HCN or NaBH4 by

Answer 9

Nucleophilic addition

Question 10

draw mechanism for reaction of a carbonyl with NaBH4

Answer 10

Nucleophilic addition,
1
Draws aldehyde/ketone with partial positive carbon and partial negative oxygen on double bond, Draws H^- nucleophile with lone pair and shows arrow from lone pair to positive carbon.
draws arrow from double bond to the oxygen to break C=O bond.

2
draws intermediate with negative oxygen ion with a lone pair, draws water molecule with partial positive hydrogens and negative oxygen.
draws arrow from oxygens lone pair to a positive hydrogen to form OH and draw arrow from that hydrogens bond to the Oxygen atom in the water.

3
forms alcohol with hydroxyl group in place of the C=O group.

Question 11

draw mechanism for reaction of carbonyl with HCN

Answer 11

Nucleophilic addition,
1
Draws aldehyde/ketone with partial positive carbon and partial negative oxygen on double bond, Draws CN^- nucleophile with lone pair on C and shows arrow from lone pair to positive carbon.
draws arrow from double bond to the oxygen to break C=O bond.

2
draws intermediate with negative oxygen ion with a lone pair, draws H^+ Ion and draws arrow from oxygens lone pair to the hydrogen to form OH group

3
forms HydroxyNitrile with hydroxyl group in place of the C=O group and a CN group on the same carbon.

Question 12

draw mechanism for reaction of haloalkane with Na OH

Answer 12

Nucleophilic substitution,
1
draws haloalkane with partial positive carbon bonded to partial negative halogen, draws OH^- nucleophile with lone pair on oxygen.
draws arrow from oxygens lone pair to positive carbon and arrow from C-Cl double bond to Cl atom.

2
draws alcohol with Hydroxyl group in place of halogen group. Draws halogen^- ion bi product

Question 13

draw mechanism for reaction of reaction of alkene with HBr

Answer 13

electrophilic addition,
1
draws Alkene, draws HBr molecule with partial positive H and partial negative Br, Draws arrow from alkene double bond to positive hydrogen

2
draws intermediate with carbocation, draws Br^- ion with lone pair
draws arrow from bromines lone pair to carbocation

3
forms bromoalkane.

Question 14

draw mechanism for reaction of alkene with Br2

Answer 14

electrophilic addition,
1
draws Alkene, draws Br2 molecule with partial positive Br closest to alkenes double bond and other partial negative Br, Draws arrow from alkene double bond to positive Br

2
draws intermediate with carbocation, draws Br^- ion with lone pair
draws arrow from bromines lone pair to carbocation

3
forms Di-bromoalkane.

Question 15

show full mechanism for electrophilic substitution of benzene.

Answer 15

using either AlCl3(friedel crafts), FebR3(bromination) or H2SO4(nitration) to form electrophile:

1:
HNO3 + H2SO4 -> NO2^+ +HSO4^- +H2O
OR
ALCl3 + CH3Cl -> AlCl4^- + CH3^+
OR
FeBr3 + Br2 -> Br^+ + FeBr4^-

2:
draws benzene and electrophile ,
draws arrow from benzenes pi ring to the electrophile and arrow starts from the carbon that will be substituted.

2.1:
draws intermediate benzene with broken pi system where the arc starts and finishes at the carbons adjacent to the involved carbon, draws hydrogen and electrophile bonded to involved carbon and an arrow from the H-C bond to the positive partial pi system.

2.2:
draws product with electrophile in place with involved carbon and a regular pi ring in benzene.

regeneration of catalyst

3:
H^+ +HSO4^- -> H2SO4
OR
FeBr4^- + H^+ -> FeBr3 + HBr
OR
H^+ + AlCl4^- -> HCl + AlCl3

Question 16

why would a molecule react electrophilic

Answer 16

if the molecule has a high electron density region ie
a double bond or pi system

Question 17

why would a molecule react nucleophilic

Answer 17

if the molecule has a low electron density region ie a carbon with polar bonds (partial carbocation)