Chapter 13

Question 1

What is the shape around a double bond

Answer 1

Carbons with double bonds are bonded to three other atoms
There are 3 groups of electron densities
Which repel as far away from each other as possible
Giving the carbons a trigonal planar shape
The bond angle around each carbon is 120

Question 2

What is a pi bond

Answer 2

The direct overlap of orbitals of 2 adjacent bonded atoms, with the electron densities above and below the plane of the bonding atoms

Question 3

Difference between sigma bonds and pi bonds densities

Answer 3

Sigma
Valence electrons are locked between the nuclei of c and the atom it bonds with

Pi
1 Valence electron is allowed to move back and forth between the double bonded atoms
Densities occupy greater space above and below the plane between the bonded atoms

Question 4

Sigma and pi bonds ability to break

Answer 4

Pi bonds electrons are not localised
Outside of the double bond
Easily intercepted
Readily breaks and undergoes addition reactions

Question 5

Why can’t pi bonds rotate

Answer 5

Pi bond locks the carbons together
Prevent from rotating
Because densities are above and below plane

Question 6

How to detect Alkenes

Answer 6

Add bromine water drop wise

Change from organe to clear - double bond is present

Question 7

Stereoisomers

Answer 7

Have the same structural formula but a different arrangement of atoms in space

Question 8

If each double bond carbon is attached to a hydrogen

Answer 8

Cis - zame zide

Trans - evade

Question 9

Hydrogenation

Answer 9

Mix alkene with hydrogen
Nickel catalyst
423k

Question 10

Halogenation

Answer 10

Mix alkene with halogen

Rt

Question 11

Hydrohalogenation

Answer 11

Bubble gaseous hydrogen halide through alkene

Rt

Question 12

Hydration

Answer 12

Mix alkene with steam

Phosphoric acid catalyst

Question 13

Électrophile

Answer 13

Atom/s that are attracted to an electron rich centre and accepts electron pairs

Question 14

Electrophilic addition mechanism

Answer 14

• the pi bond electrons are attracted to the partially positive hydrogen causing carbon double bond to break
• sigma bond forms between hydrogen in H-Br and the carbon that was in the double bond
• h-br breaks heterolytically - electron pair goes to Br
• producing a br ion and positive carbocation
• br ion reacts with carbocation

Question 15

Electrophilic addition mechanism with non polar molecules

Answer 15

• Pi bond electrons polarise the br-br bond by repelling its electrons, making an induced dipole
• Pi electrons are attracted to partially positive Br + end, causing carbon double bond to break
• forming a sigma bond between the br and carbon
• br - br bond breaks heterolyticalky with the electron pair going to the Br- end
• producing a carbocation and br ion
• they react to form the addition product of the reaction

Question 16

Which isomer will be produced in the largest amount

Answer 16

The hydrogen halide that reacts with the most stable carbcation

Question 17

What makes a carbocation stable

Answer 17

The carbocation with the most alkyl groups attached
Alkyl groups have an electron donating effect
They push electrons towards the positive charge causing the positive charge to spread
The more it spreads the more stable it is