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Chemistry > Alkenes > Flashcards

Alkenes Flashcards

1
Q

Alkenes:

What are Alkenes?

A

Unsaturated HC

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2
Q

Alkenes: Bonds in Organic Molecules

When are Covalent Bonds formed?

A

When atomic orbitals from diff atoms overlap
↳ electrons are shared

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3
Q

Alkenes: Bonds in Organic Molecules

Why is a Covalent Bond formed?

A

Nuclei of the atoms are attracted by electrostatic attraction to the bonding electrons

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4
Q

Alkenes: Bonds in Organic Molecules

What are Sigma Bonds?

(σ-bond)

A

Single Covalent bonds in organic mol

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5
Q

Alkenes: Bonds in Organic Molecules

How is a Sigma Bond formed?

A

When 2 orbitals overlap in a straight line between 2 atoms

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6
Q

Alkenes: Bonds in Organic Molecules

Why do Sigma Bonds have a High Bond Enthalpy?

A

There’s a strong electrostatic attraction between the nuclei & shared electrons
↳ they’re the strongest Covalent Bond

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7
Q

Alkenes: Bonds in Organic Molecules

Why are Sigma Bonds strong?

A

There is a high electron density between the nuclei & shared electrons

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8
Q

Alkenes: Bonds in Organic Molecules

What is a Double Covalent bond made up of?

A
  • Pi Bond
  • Sigma Bond
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9
Q

Alkenes: Bonds in Organic Molecules

How is a Pi Bond formed?

A

2 lobes of 2 orbitals overlap sideways
↳ 1 above & 1 below

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10
Q

Alkenes: Bonds in Organic Molecules

Why are Pi Bonds weaker?

A

They have a low electron density between the nuclei & shared electrons
↳ spread out above & below

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11
Q

Alkenes:

Why can’t double bonds rotate?

A

They’re arranged to be Trigonal Planar

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12
Q

Alkenes: Stereoisomerism

What is Stereoisomerism?

A

Compounds with the same structural formula but different arrangement in space

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13
Q

Alkenes: Stereosiomerism

Where is the C=C located in an Alkene?

A

In the longest chain

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14
Q

Alkenes: Stereosiomerism

When is E/Z used?

A

When each carbon have 2 different groups attached to them

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15
Q

Alkenes: Stereosiomerism

What is an E-Isomer?

A

When the same priority groups positioned diagonally

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16
Q

Alkenes: Stereosiomerism

What is an Z-Isomer?

A

When the same priority group are on the same side of the double bond

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17
Q

Alkenes: Stereosiomerism

What are Priority Groups?

A

Compound w a higher atomic number are given higher priority

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18
Q

Alkenes: Stereosiomerism

Why are Priority Groups used?

A
  • To figure out the name of the molecule
  • To figure out which E/Z isomer it is
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19
Q

Alkenes: Stereosiomerism

How do u work out the Priority Group if the C is directly bonded to 2 other C?

A

The group bonded w more C has higher priority

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20
Q

Alkenes: Stereosiomerism

What do u look for in Cis-Trans Isomers?

A

How identical groups are positioned

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21
Q

Alkenes: Stereosiomerism

When do you use Cis-Trans Isomerism?

A

When there’s at least 1 common group on the compound

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22
Q

Alkenes: Stereosiomerism

What is Cis Isomerism?

(same)

A

When the identical groups are on the same side of the double bond

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23
Q

Alkenes: Stereosiomerism

What is Trans Isomerism?

(different)

A

When the identical groups are on opposite sides of the double bond

24
Q

Alkenes: Reaction of Alkenes

What is Electrophillic Addition?

A

When the double bond opens up & atoms are added to the C atoms

25
Q

Alkenes: Reaction of Alkenes

What does the C=C contain?

A

Its rich in electrons : it attracts electrophiles (something that is + or δ+)

26
Q

Alkenes: Reaction of Alkenes

What is Hydrogeneration?

Alkene + Hydrogen → Alkane

A

Adding hydrogen to C=C bond produces an alkane
* Margerene is made

27
Q

Alkenes: Reaction of Alkenes

What is Steam Hydration?

Alkene + Water → Alcohol

A

Adding steam to an alkene to form an alcohol
* 300°C
* 60 atm
* Phosphoric Acid Catalyst

28
Q

Alkenes: Reaction of Alkenes

Alkenes are Oxidised by Acidified Potassium Manganate (VII)

A

The purple colour of K becomes decolourised making a diol
↳ alcohol that has 2 OH groups

29
Q

Alkenes: Reaction of Alkenes

Halogens React w Alkenes to form Dihalogenoalkanes

(Beginning)

A
  • Alkene moves towards Br
    ↳ causing them to repel
  • But if pushing force > repulsion
    ↳ Br becomes polarised → e- from Br moves to the 2nd Br : induces a polar bond
30
Q

Alkenes: Reaction of Alkenes

Halogens React w Alkened to form Dihalogenoalkanes

(Intermediate)

A
  • C=C breaks as its attracted to Br
  • Br bond is broken
31
Q

Alkenes: Reaction of Alkenes

Halogens React w Alkenes to form Dihalogenoalkanes

(End)

A
  • Place Br by a C atom
    ↳ C has 4 bonds
  • Add a + to the other carbon
    ↳ creating a C+ cation
  • But there’s still a free Br-
    ↳ attaches to C+
32
Q

Alkenes: Alkenes undergo Addition with Hydrogen Halides

How are Halogenoalkanes formed?

(equation)

A
33
Q

Alkenes: Markownikoff & Carboncation Stability

How do you workout if a Carboncation is Primary,Secondary or Tertiary?

A
  • Locate C+ cation
  • Look for how many alkyl groups are attached to it
34
Q

Alkenes: Markownikoff & Carboncation Stability

What is an Alkyl Group?

(R)

A

An alkane w one less H

35
Q

Alkenes: Markownikoff & Carboncation Stability

What is a Primary Carboncation?

A

C+ cation is only 1 attached alkyl group

36
Q

Alkenes: Markownikoff & Carboncation Stability

What is a Secondary Carboncation?

A

C+ cation is attached to 2 alkyl groups

37
Q

Alkenes: Markownikoff & Carboncation Stability

What is a Tertiary Carboncation?

A

C+ cation is attached to 3 alkyl groups

38
Q

Alkenes: Markownikoff & Carboncation Stability

How would you stabilise a Carboncation?

A

By donating electrons through attaching more alkyl groups

The more alkyl groups, the more stable : the longer that reaction as + & + make bonds quicker

39
Q

Alkenes: Markownikoff & Carboncation Stability

How would you determine which product is Major/Minor?

A

Major: Most stable product
Minor: Less stable product

40
Q

Alkenes: Polymers

Whats a Monomer?

A

A small unit

41
Q

Alkenes: Polymers

What is a Polymer?

A

Long chains

42
Q

Alkenes: Polymers

What is Addition Polymerisation?

monomer → repeat unit → polymer

A

When the alkene double bond breaks & joins together into polymers

43
Q

Alkenes: Different methods for Disposing Polymers

How are Waste Plastics Buried?

A

Landfill only when the plastic is difficult to separate or recycle

44
Q

Alkenes: Different methods for Disposing Polymers

What is an Advantage of Burying Waste Plastics?

A

Easily removed

45
Q

Alkenes: Different methods for Disposing Polymers

What is a Disadvantage of Burying Waste Plastics?

A

Space used for vegetation is used up

46
Q

Alkenes: Different methods for Disposing Polymers

How are Waste Plastics Reused?

A
  • Many plastics are made from non-renewable sources so they’re reused
  • Some are re-moulded into others
    ↳ cracked into monomers or used as feedstock
47
Q

Alkenes: Different methods for Disposing Polymers

What are the Advantages of Cracking Waste Plastics?

A

Forms alkenes
↳ new useful plastics

48
Q

Alkenes: Different methods for Disposing Polymers

What are the Disadvantages of Cracking Waste Plastics?

A

High heat is needed for cracking → higher costs
↳ other chemicals released

49
Q

Alkenes: Different methods for Disposing Polymers

What are the Advantages of Remoulding?

A

New objects are formed

50
Q

Alkenes: Different methods for Disposing Polymers

What are the Disadvantages of Remoulding?

A

Time consuming

51
Q

Alkenes: Different methods for Disposing Polymers

How are Waste Plastics Burned?

A

Last Resort: heat generated can be used for electricity
↳ releases toxic gases such as HCl

52
Q

Alkenes: Different methods for Disposing Polymers

What are the Advantages of Burning Waste Plastics?

A

Heat is given off

53
Q

Alkenes: Different methods for Disposing Polymers

What are the Disadvantages of Burning Waste Plastics?

A

Non-reusable source used e.g oil
↳ releases emissions

54
Q

Alkenes: Sustainability

What is Sustainability?

A

Saving something for the long term usage

55
Q

Alkenes: Sustainability

How to ensure the Design of Suitable Polymers?

A
  • Use molecules that are safe & environmentally friendly
  • Use renewable where possible
  • Use minimum amount of energy
  • Limit waste products
56
Q

Alkenes: Sustainability

What are Biodegradable Polymers?

A

Polymers that break down naturally

57
Q

Alkenes: Sustainability

What are the Advantages of using Renewable Materials?

A
  • They won’t run out
  • They’re carbon neutral

Chemistry (13 decks)

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