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AS CHEM UNIT2 > 2.4 Hydrocarbons > Flashcards

2.4 Hydrocarbons Flashcards

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1
Q

What is a hydrocarbon?

A

A compound of hydrogen and carbon only

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2
Q

What is a homologous series?

A

A family of compounds with the same functional group

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3
Q

What is a functional group?

A

Group of atoms responsible for properties

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4
Q

Define a structural isomer

A

Same molecular formula but different structural formula

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5
Q

Define a positional isomer

A

Same molecular formula but different arrangement of functional group

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6
Q

Name the chains 1-10

A
  • methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane
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7
Q

What are the different types of organic formula?

A
  • structural: say it as you see it is CH3CH2CH2OH
  • display: draw out every bond
  • molecular: simplest collation of each element
  • empirical: simplest whole number ratio
  • skeletal: backbone where hydrogens are assumed and functional groups bolted
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8
Q

Define aliphatic and aromatic

A
  • aliphatic: straight chain
  • aromatic: cyclic structures
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9
Q

What are the naming rules?

A
  1. Longest C chain for parent
  2. Identify parent functional group
  3. Organise functional groups alphabetically
  4. Number position of function groups, lowest possible
  5. Dashes between letters and numbers, commas between numbers
  6. Piece it all together
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10
Q

Alkane functional group

A
  • ane
  • C-C
  • CnH2n+2
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11
Q

Alkene functional group

A
  • ene
  • double bond C
  • CnH2n
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12
Q

Halogenoalkanes functional group

A
  • fluoro/chloro/bromo/iodo-
  • R-X (attached to C anywhere in chain)
  • CnH2n+1X
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13
Q

Alcohols functional group

A
  • ol
  • R-OH
  • CnH2n+1OH
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14
Q

Aldehyde functional group

A
  • al
  • R-C double bond O top, H bottom
  • R-CHO
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15
Q

Ketone functional group

A
  • one
  • double bond O anywhere in chain
  • R-CO-R
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16
Q

Carboxylic acid functional group

A
  • oic acid
  • R-C double bond O on top, OH bottom
  • R-COOH
17
Q

Would a straight carbon chain or cross linked carbon chain have the highest boiling point?

A
  • straight chain isomers have more points of contact than cross linked so more VdW interaction and therefore more energy to break
18
Q

Reactions of alkanes

A
  • very unreactive as saturated
  • radical substitution
19
Q

Define a radical

A

A species with an unpaired electron

20
Q

Explain the stages of radical substitution

A

Initiation: UV rays break molecules apart by homolytic bind fission. 1 electron to each atom to make 2 independent radicals

Propagation: reaction with radical and starting molecule

Termination: process ends when radical reacts with radical

21
Q

Explain the bonding in alkenes

A
  • carbon double bond made of one sigma bind and one pi bond
  • caused by P-orbitals overlapping resulting in areas of high electron density known as a pi cloud
22
Q

How can you make alkenes?

A
  • heat with platinum or do elimination reaction
  • catalytic cracking ( useless long chain hydrocarbons made into shorter more useful ones )
23
Q

Define an electrophile

A

An electron loving species with a positive charge

24
Q

Define a nucleophile

A

A nuclei loving species with a -ve charge

25
Q

How do you test for alkenes?

A
  • add bromine
  • decolourises
26
Q

Outline electrophilic addition for C2H4 and Br2

A
27
Q

Explain isomerism in alkenes

A
  • 2 stereoisomers are formed - same structural formula but different arrangement of atoms in space
  • 2 conditions needed: C=C, two diff groups of atoms on each carbon
28
Q

How to make alcohols with alkenes

A
  • add H20, steam form
  • 60atm, 300°C, H3PO4 catalyst
29
Q

How to make alkanes from alkenes

A
  • add H2
  • 150°C, nickel/platinum catalyst
30
Q

Explain why ethanol is soluble in water but ethanol is not

A

Ethanol can form hydrogen bonds with water molecules whereas ethane cannot

31
Q

Explain E and Z isomers

A

E: opposite
Z: same

32
Q

Describe bonding in alkenes and use this to explain its reactivity

A
  • C=C double bond of one sigma and one pi
  • sigma made by overlap of s orbitals, pi by overlap of p orbitals that creates areas of high electron density known as pi cloud
  • makes them susceptible to electrophilic attack leading to addition reactions
33
Q

What feature of a molecule gives rise to EZ isomerism

A

C=C bond

34
Q

Reagents for elimination reaction

A
  • NaOH in ethanol
  • heat
35
Q

How to distinguish between cyclohexane and hexene

A
  • add bromine water
  • hexene decolourises bromine water but cyclohexane does not
36
Q

Additional reagents to test for alkenes

A

Potassium manganate

AS CHEM UNIT2 (7 decks)

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