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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
# **Alkenes:** Reaction of Alkenes What does the C=C contain?
Its rich in electrons **:** it attracts electrophiles (something that is + or δ+)
26
# **Alkenes:** Reaction of Alkenes What is Hydrogeneration? | Alkene + Hydrogen → Alkane
Adding hydrogen to C=C bond produces an alkane * Margerene is made
27
# **Alkenes:** Reaction of Alkenes What is Steam Hydration? | Alkene + Water → Alcohol
Adding steam to an alkene to form an alcohol * 300°C * 60 atm * Phosphoric Acid Catalyst
28
# **Alkenes:** Reaction of Alkenes Alkenes are Oxidised by Acidified Potassium Manganate (VII)
The purple colour of K becomes decolourised making a diol ↳ alcohol that has 2 OH groups
29
# **Alkenes:** Reaction of Alkenes Halogens React w Alkenes to form Dihalogenoalkanes | (**Beginning**)
* 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
# **Alkenes:** Reaction of Alkenes Halogens React w Alkened to form Dihalogenoalkanes | (**Intermediate**)
* C=C breaks as its attracted to Br * Br bond is broken
31
# **Alkenes:** Reaction of Alkenes Halogens React w Alkenes to form Dihalogenoalkanes | (**End**)
* 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
# **Alkenes:** Alkenes undergo Addition with Hydrogen Halides How are Halogenoalkanes formed? | (equation)
33
# **Alkenes:** Markownikoff & Carboncation Stability How do you workout if a Carboncation is Primary,Secondary or Tertiary?
* Locate C+ cation * Look for how many alkyl groups are attached to it
34
# **Alkenes:** Markownikoff & Carboncation Stability What is an Alkyl Group? | (R)
An alkane w one less H
35
# **Alkenes:** Markownikoff & Carboncation Stability What is a Primary Carboncation?
C+ cation is only 1 attached alkyl group
36
# **Alkenes:** Markownikoff & Carboncation Stability What is a Secondary Carboncation?
C+ cation is attached to 2 alkyl groups
37
# **Alkenes:** Markownikoff & Carboncation Stability What is a Tertiary Carboncation?
C+ cation is attached to 3 alkyl groups
38
# **Alkenes:** Markownikoff & Carboncation Stability How would you stabilise a Carboncation?
By donating electrons through attaching more alkyl groups ## Footnote The more alkyl groups, the more stable **:** the longer that reaction as + & + make bonds quicker
39
# **Alkenes:** Markownikoff & Carboncation Stability How would you determine which product is Major/Minor?
**Major:** Most stable product **Minor:** Less stable product
40
# **Alkenes:** Polymers Whats a Monomer?
A small unit
41
# **Alkenes:** Polymers What is a Polymer?
Long chains
42
# **Alkenes:** Polymers What is Addition Polymerisation? | monomer → repeat unit → polymer
When the alkene double bond breaks & joins together into polymers
43
# **Alkenes:** Different methods for Disposing Polymers How are Waste Plastics Buried?
Landfill only when the plastic is difficult to separate or recycle
44
# **Alkenes:** Different methods for Disposing Polymers What is an Advantage of Burying Waste Plastics?
Easily removed
45
# **Alkenes:** Different methods for Disposing Polymers What is a Disadvantage of Burying Waste Plastics?
Space used for vegetation is used up
46
# **Alkenes:** Different methods for Disposing Polymers How are Waste Plastics Reused?
* 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
# **Alkenes:** Different methods for Disposing Polymers What are the Advantages of Cracking Waste Plastics?
Forms alkenes ↳ new useful plastics
48
# **Alkenes:** Different methods for Disposing Polymers What are the Disadvantages of Cracking Waste Plastics?
High heat is needed for cracking → higher costs ↳ other chemicals released
49
# **Alkenes:** Different methods for Disposing Polymers What are the Advantages of Remoulding?
New objects are formed
50
# **Alkenes:** Different methods for Disposing Polymers What are the Disadvantages of Remoulding?
Time consuming
51
# **Alkenes:** Different methods for Disposing Polymers How are Waste Plastics Burned?
**Last Resort:** heat generated can be used for electricity ↳ releases toxic gases such as HCl
52
# **Alkenes:** Different methods for Disposing Polymers What are the Advantages of Burning Waste Plastics?
Heat is given off
53
# **Alkenes:** Different methods for Disposing Polymers What are the Disadvantages of Burning Waste Plastics?
Non-reusable source used e.g oil ↳ releases emissions
54
# **Alkenes:** Sustainability What is Sustainability?
Saving something for the long term usage
55
# **Alkenes:** Sustainability How to ensure the Design of Suitable Polymers?
* Use molecules that are safe & environmentally friendly * Use renewable where possible * Use minimum amount of energy * Limit waste products
56
# **Alkenes:** Sustainability What are Biodegradable Polymers?
Polymers that break down naturally
57
# **Alkenes:** Sustainability What are the Advantages of using Renewable Materials?
* They won't run out * They're carbon neutral

Chemistry (13 decks)

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