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chemistry > Chapter 13(approved) > Flashcards

Chapter 13(approved) Flashcards

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1
Q

What type of alkenes have the general formula CnH2n?

A

Aliphatic alkenes that contain one double bond

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2
Q

What happens to the carbon outer shell electrons in a double bond?

A

For each carbon atom in the double bond, three of the four electrons are used in three sigma bonds, one to each of the three atoms it is bonded to, and one is used in pie bonds

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3
Q

Which electrons form a pie bond?

A

The one electron from each of the double bonded carbon atoms which isn’t bonded to other atoms

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4
Q

What forms a pie bond?

A

The sideways overlap of two adjacent p-orbitals, above and below the bonding Carbon atoms

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5
Q

Where is the electron density in a pie bond

A

In a pie bind the electron density is concentrated above and below the bonding region of the double bond

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6
Q

How does the pie bond affect the rotation of the molecule?

A

The pie bond locks the two carbons in position and prevents them from rotating around the double bond

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7
Q

What is the shape and bond angle around each carbon atom in the double bond and why?

A

Trigonal planar, 120 degree bond angle, 3 bonding pairs 0 lone pairs, bonding pairs repel each other equally

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8
Q

Stereoisomers

A

A molecule with the same structural formula but different arrangement of atoms in space

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9
Q

Why does stereoisomerism arise around double bonds

A

Because rotation around double bonds is restricted due to the pie bond’s electron density above and below the plane of the sigma bond, so the groups attached to each carbon atom are fixed relative to each other

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10
Q

What are the conditions of E/Z isomerism?

A

A C=C double bond
Different groups attached to each carbon atom of the double bond

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11
Q

What is cis-trans isomerism?

A

A special case of E/Z isomerism, with the same conditions: a C=C double bond and different groups attached to each carbon atom, but in cis-trans, one of the attached groups of each carbon atom must be hydrogen

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12
Q

How are cis-trans isomers classified

A

The atoms attached to each carbon atom are given a priority based on their atomic number

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13
Q

Z/Cis isomer conditions

A

High priority group on the same side of the double bond

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14
Q

E/trans isomer conditions

A

If the high priority group is on opposite sides of the double bond

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15
Q

Why are alkenes much more reactive than alkanes?

A

Because of the presence of the pie bond, which is on the outside of the double bond, so it is more exposed than sigma bonds and therefore more easily broken, allowing alkenes to take part in addition reactions quite easily

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16
Q

Alkenes to alkanes reactants and conditions

A

Alkenes react with hydrogen in the presence of a metal catalyst like Nickel to form alkanes

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17
Q

Alkenes to dihaloalkanes reactants and reaction conditions

A

Alkenes react with halogens to form with dihaloalkanes

18
Q

Test for alkenes

A

Add bromine water, if alkenes are present, solution should decolourise as it forms a dihaloalkane

19
Q

Alkenes to haloalkanes reactants and conditions

A

Add hydrogen halides to alkenes to form haloalkanes

20
Q

Alkenes to alcohols reactants and conditions

A

Alkenes and steam react in the presence of an acid catalyst like phosphoric acid to form alcohols

21
Q

What is the reaction mechanism for alkenes taking part in an addition reaction to form saturated compounds called?

A

Electrophilic addition

22
Q

Why does the double bond in an alkene represent a region of high electron density?

A

Because of the presence of the pie electrons

23
Q

What does the high electron density of the pie electrons do?

A

Attracts electrophiles

24
Q

Electrophile

A

An electron pair acceptor

25
Q

How are carbocations classified?

A

Primary, secondary or tertiary based on how many akyl groups are ttached to them

26
Q

Which carbocations are most stable and why?

A

Tertiary carbocations are the most stable as there are more akyl groups, so the postive charge of the carbocations is spread out more

27
Q

Major product

A

The product with the greater yield of the two, determined by which product has a more stable carbocation

28
Q

Conditions for there to be a minor and major product

A

Both reactant molecules have to be unsymmetrical

29
Q

polymers

A

Extremely large molecules made from many thousands of repeat units

30
Q

What is addition polymerisation?

A

A process which unsaturated alkene molecules undergo to form long saturated chains containing no double bonds

31
Q

Positive and negative effects of polymers lack of reactivity

A

+ They can store food and chemicals
- Challenging to dispose of

32
Q

What is the effect of recycling polymers?

A

Reduces their environmental impact by:
- conserving finite fossil fuels
- decreases the amount of waste going to landfill

33
Q

Why is PVC recycling and disposal hazardous and how is it recycled?

A

PVC hypha’s high chlorine content and releases polluants when burnt like HCl which is corrosive

PVC is dissolved by a solvent, and high grade PVC is recovered by preciptation from the solvent

34
Q

Feedstock recycling explanation, and an advantage of it

A

The chemical and thermal process that can reclaim monomers, gases or oils from waste polymers which can be used as raw materials for the production of new polymers

Advantage: It is able to handle unsorted and unwashed polymers

35
Q

Bioplastics: what are they produced from and what is their advantage?

A

Plant startch, cellulose, plant oils and proteins

They offer a renewable and sustainable alternative to oil based products

36
Q

What happens to biodegradeable polymers?

A

Thy can be broken down into water, carbon dioxide and biological compounds

37
Q

What are photodegradable polymers?

A

Polymers whose bonds can be weakened by absorbing light

38
Q

How can HCl be removed from waste gases produced in combustion?

A

Bubbling it through an alkali

39
Q

Give three ways by which waste polymers can be processed to save resources

A

Recycling
Used as an organic feedstock (which is a raw material for manufacturing)
Used as an alternative to fossil fuels

40
Q

Benefits for sustainability of processing waste polymers by combustion (using them as fuel)

A

They have a high stored energy value, so they are able to produce heat which can generate electricity

41
Q

One problem with the disposal of waste polymers by combustion

A

Hydrochloric acid is formed

42
Q

Two reasons why using a lower temperature is beneficial to the environment

A

Less CO2 emissions

Less fossil fuels are consumed

chemistry (12 decks)

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