Bonding, Alkenes, Isomers Flashcards

1
Q

What are the two types of bonds?

A

Pi and Sigma bonds

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2
Q

What is more common Pi or Sigma?

A

Sigma bonds

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3
Q

What is a sigma bond?

A

Sigma bonds are the strongest type of covalent bond. All single bonds and the first part of double or triple bonds are sigma bonds

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4
Q

What is a Pi bond?

A

The second and third part of a triple bond or the second part of a double bond. The Pi bond is not directly between the nuclei so is weaker than a Sigma bond.

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5
Q

What do the solid and dashed wedges represent when it comes to representing a 3D molecule

A

-wedges are the bonds going away from the plane of the paper
-dashes are the bonds coming towards the plane of the paper

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6
Q

How does Ethene become 1,2-dibromoethane?

A

Through electrophilic addition at room temperature and pressure when Bromine (aq) is added to ethene

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7
Q

How does ethene become 1chloroethane when HCl (aq) is added?

A

Through electrophilic addition under RTP and the addition of HCl (aq)

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8
Q

What two ways does ethene become ethane?

A
  1. Through addition with an Ni catalyst and H2 (g) at High temperature and pressure
  2. With a Pt catalyst and H2 (g) at room temperature and pressure
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9
Q

How does ethene become ethanol?

A

Through electrophilic addition with the H3PO4 and H2O (g) at high temperature and pressure

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10
Q

Describe alkenes reactions with halogens

A

Alkenes react with halogens at RTP.

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11
Q

Describe the Bromine test for halogens

A
  • add a few drops of bromine water Br2(aq) to an alkene and shake well
  • if the compound contains a carbon carbon double bond (unsaturated) there will be a colour change from orange to colourless
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12
Q

Describe the electrophilic addition mechanism

A
  1. The partially positive bromine atom accepts a pair of electrons from the carbon carbon double bond
  2. The Br-Br bond breaks
  3. This leaves a carbocation intermediate which is unstable and quickly reacts with the Br- from the broken Br-Br bond
    The final product is formed
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13
Q

Define electrophile

A

An electrophile is a positive ion or molecule with a partially positive region which is attracted to a negative region in a molecule, which reacts by accepting a pair of electrons forming a covalent bond.

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14
Q

Define addition reaction

A

Addition reactions are when 2 molecules react to give just 1 product molecule (by combining together)

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15
Q

What would happen if an unsymmetrical alkene was used in an electrophilic addition reaction (like propene)?

A

There would be two products on two/ or more different carbons

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16
Q

How can converting an alkene into an alkane be used?

A
  • to find out how many double bonds an alkene has
  • hydrogenation of vegetable oils to convert them into margarine since carbon carbon bonds have a higher mp than carbon carbon double bonds
17
Q

What are the two types of isomerism?

A

-structural isomers molecules with the same molecular formula but different structural formulas
-steroisomerism molecules with the same molecular formula but atoms point a different way in space (E/Z isomerism)

18
Q

MAGIC SENTENCE
What is required for a molecule to have E/Z isomerism?

A
  • a carbon carbon double bond which cannot rotate
  • each carbon in the carbon carbon double bond must be bonded to 2 different atoms or groups