chapter 13

Question 1

the nature of the double bond

Answer 1

-a pi bond is formed by the sideways overlap of 2 p orbitals
-region of electron density is concentrated above and below the line of the bonding atoms
-pi bond locks the 2 carbon atoms in position and prevents them from rotating around the double bond
120 degrees

Question 2

stereoisomers

Answer 2

same structural formula but a diff arrangement of atoms in space.

Question 3

E/Z isomerism

Answer 3

arises because rotation about the double bond is restricted and groups are fixed relative to each other

Question 4

what must a molecule have to show E/Z isomerism

Answer 4

must have:

• a c-c double bond
• different groups attached to each carbon of the double bond

Question 5

cis-trans isomerism

Answer 5

special case of E/Z isomerism

• one of the attached groups on each carbon atom in the double bond must be hydrogen
• cis is Z isomer
• trans is E isomer

Question 6

hydrogenation of alkenes conditions

Answer 6

hydrogen, nickel catalyst, 423K

Question 7

hydration of alkenes conditions

Answer 7

steam in the presence of phosphoric acid catalyst, H3PO4

Question 8

an electrophile

Answer 8

an atom or group of atoms that is attracted to an electron rich centre and accepts an electron pair. usually a positive ion or a molecule containing an atom w/ a partial positive charge

Question 9

Markownikoff’s rule

Answer 9

when a hydrogen halide reacts w/ an unsymmetrical alkene the hydrogen of the hydrogen halide attaches itself to the carbon atom with a greater number of hydrogen atoms and a smaller number of carbon atoms

Question 10

carbocation stability

Answer 10

• linked to electron-donating ability of alkyl group
• each alkyl group pushes electrons towards the positive charge of the carbocation.
• positive charge is spread over the alkyl groups, the more alkyl groups= more spread out charge= more stable
• addition of a hydrogen halide form s a major product via the most stable carbocation

Question 11

recycling polymers

Answer 11

-reduces environmental impact- conserves fossil fuels & decreases waste to landfill

Question 12

PVC recycling

Answer 12

• hazardous due to high chlorine content & additives
• landfill not sustainable
• when burnt releases hydrogen chloride, corrosive gas & other pollutants
• new technology uses solvents to dissolve the polymer, high grade PVC is then recovered by precipitation from the solvent

Question 13

using waste polymers as fuel

Answer 13

• difficult to recycle

- incinerated to produce heat generating electricity

Question 14

feedstock recycling

Answer 14

the chemical and thermal processes that can reclaim monomers, gases or oil from waste polymers. These materials can be used as raw materials for production of new polymers
+able to handle unwashed & unsorted polymers

Question 15

biodegradable polymers

Answer 15

broken down by micro-organisms into water, CO2 and biological compounds
-usually made from starch or cellulose

Question 16

photodegradable polymers

Answer 16

contain bonds that are weakened by absorbing light- being developed