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A Level Chemistry: Organic Chemistry > Chapter 14: Alkenes > Flashcards

Chapter 14: Alkenes Flashcards

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1
Q

What type of hydrocarbon is Alkenes

A
  • Unsaturated Hydrocarbon
  • Has 1 or more double bonds
  • Double bond makes them more reactive as there is a high concentration of electrons ( high electron density) around double bond.
    • Makes more bonds with extra atoms.
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2
Q

What is the general formula of Alkenes

A
  • CnH2n
  • Only contains Carbon and Hydrogen
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3
Q

What is the shape of alkenes

A
  • Flat/planar molecule
  • No rotation about the double bond.
  • There is a p-orbital containing a single electron on each carbon.
    • They overlap to form a cloud of electron density above and below the bond called π bond.
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4
Q

What are the 2 types of isomers of Alkenes

A
  • Position
  • Geometrical
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5
Q

What are Position Isomers

A
  • Double bond in different positions in the carbon chain
  • But-1-ene, But-2-ene
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6
Q

What are Geometrical Isomers

A
  • Same structural formula but bonds are arranged differently
  • Occurs around C=C bond. E/Z Notation based on atomic number.
  • Z - But-2-ene (same side) and E - But-2-ene (different sides)
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7
Q

How do Alkenes react

A
  • The C=C bond forms an electron rich area and can be attacked by positively charged reagents (electrophiles - electron pair acceptors)
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8
Q

What is the Electrophilic Addition reaction between Alkenes and Hydrogen Halide (HBr)

A
  • Double bond repels electrons in HBr
  • The electrophile is attracted
  • The Br is more electronegative than H so is polar. Electrons are drawn towards Br.
  • H-Br bond breaks heterolytically.
  • Forms a carbocation.
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9
Q

What is the Electrophilic Addition reaction between Alkenes and Halogens (Br2) and conditions

A
  • Conditions: Aqueous
  • Double bond repels electrons in Br2
  • Br attracted to double bond and repels electrons to the other Br
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10
Q

What is the Electrophilic Addition reaction between Alkenes and Concentrated Sulfuric Acid (H2SO4) and conditions

A
  • Conditions: cold, conc, room temp
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11
Q

What is the Electrophilic Addition reaction between Water and Alkenes

A
  • Conditions: Strong aqueous, acid catalyst
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12
Q

What are major and minor products and how are they formed and which one is more stable

A
  • Alkyl groups release electrons (positive inductive effect)
  • This stabilises the positive charge of intermediate carbocation
  • Tertiary carbocation is more stable than primary carbocation as it has 3 alkyl groups attcahed to the C+ of carbocation.
  • Major is more stable than minor
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13
Q

How to test for Unsaturation in Alkenes

A
  • Shake an alkene with orange bromine water
  • Solution turns from orange to colourless (decolourises)
  • Bromine is added to double bond to form colourless dibromoalkane (electrophilic addition)
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14
Q

What are Polymers

A
  • Long chain molecules formed when lots of small monomers are joined
  • E.g DNA, Starch, Proteins, Cellulose
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15
Q

How are Addition Polymers formed

A
  • Made from monomers with carbon carbon double bond
  • Can be formed from alkene or substituted alkene (H replaced by another atom)
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16
Q

How do you name Addition Polymers

A
  • Poly (x)
  • X = name of monomer
17
Q

What are the Properties of polymers

A
  • Polymers are saturated = unreactive
  • Monomers within a polymer chain have strong covalent bonds - however intermolecular forces are weaker. Longer chains with fewer branches have stronger intermolecular forces (more strong and rigid
18
Q

What is PolyChloroethene and what are its typical uses

A
  • Covalent bonds between carbon and chlorine are polar. Permanent dipole-dipole forces between chains make it hard and brittle
  • Used in drainpipes and window frames
19
Q

What are Plasticisers and what are the uses of plasticised PVC

A
  • Adding chemicals (plasticisers) to modify properties
  • Get between polymer chains and push them apart
  • Reduces strength of intermolecular forces causes chains to slide and bend
  • Plasticised PVC is more flexible than Rigigid PVC and used in flooring tiles, electrical cable insulation and clothing.

A Level Chemistry: Organic Chemistry (12 decks)

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