Topic 5 (Alkene mechanisms and Polymers)

for mechanism of (asymmetric) alkene reacting with HBr/HCl/HF, where does Br attack to form major product?

• for major products, they will attack the most stable carbocation, or the carbon bonded to more carbons
  (hydrogen bonds to the other less stable Carbocation)

alkyl groups are _____

alkyl groups are electron giving groups, always gives electron to carbocation

What does the curly arrows shown represent ?

movement of pair of electron from a bond to an atom, forming ion

bromine water test (add bromine solution)

propane = remains orange solution
(substitution)

propene = turns colorless
(as an alkene undergoes addition with bromine and thus makes solution colorless)

NOTE:
for both test for alkane and alkene → two layer forms
( bottom water and top orange if alkane/ colorless if alkene )

what feature of pi bond allows sterioisomerism (E Z )

π bond gives restricted rotation around the C=C double bond.

complete combusion products and incomplete combustion products

CxHy + O2 → CO2 + H20

CxHy + O2 → C + H20 [ OR CO + H20]

Describe 2 differences between orbital overlap of sigma and pi bond between carbon atoms

• sigma bond has 1 area of orbital overlap(or electron cloud) but pi bond has 2
  
  

• sigma bond has head on overlap but pi bond has sideways overlap

(look at diagram, sigma has 1 area of orbital overlap while pi got 2)

pi bond from C=C broken and sigma bond from H-H is broken

sigma bond formed between C-H

NOTE:

stability of compound does not determine which product is formed, rather it is the stabitlity of carbocation

What reagent and condition is needed to make chloroethane from ethane

reagent = chlorine /Cl2
condtion = UV light

why does making chloroethane with ethene give more percentage yield than with ethane

it is an addition reaction that producesonly one product

give 3 factors that need to be considered before deciding which aterial to use such as metal and PVC for long term sustainable use.

• biodegradeable

• availability

• renewable or non-renewable source

what is an electrophile?

define free radical

a species that can accept a pair of electrons to form covalent bond
(species that is attracted to a region of high electron density)

Free radical is a species that contains an unpaired electron

The mechanisms shown of ther reaction is an example of what?

electrophilic addition

name the mechanisms:

alkane + halogen

alkene + halogen

alkane + halogen = free radical substitution

alkene + halogen = electrophilic addition