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a level chemistry > Module 4.1 - Basic Concepts and Hydrocarbons > Flashcards

Module 4.1 - Basic Concepts and Hydrocarbons Flashcards

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1
Q

What is a homologous series?

A

A series of organic compounds having the same functional group but with each successive member differing by CH2.

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2
Q

What is a functional group?

A

A group of atoms responsible for the characteristic reactions of a compound.

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3
Q

What are aliphatic hydrocarbons?

A

A compound in which carbon atoms are joined together either straight unbranched/branched chains.

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4
Q

What are alicyclic hydrocarbons?

A

A compound in which carbon atoms are joined together in a ring structure but not aromatic (no benzene ring).

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5
Q

What are aromatic hydrocarbons?

A

A compound in which there is at least one benzene ring in the structure.

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6
Q

What is the difference between a alkyl and alkane with the same number of carbon atoms? General formula of alkyls?

A

one less H - C(n)H(2n+1)

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7
Q

What is the formula of propyl?

A

C3H7

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8
Q

What is the formula for propane?

A

C3H8

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9
Q

­­­­­What is the functional group and suffix of alkanes?

A

> Functional group : C-C

> Suffix: -ane

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10
Q

What is the functional group and suffix of alkenes?

A

> Functional group: C=C

> Suffix: -ene

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11
Q

What is the functional group, prefix and suffix of alcohols?

A

> Functional group: -OH
Prefix: Hydroxy-
Suffix: -ol

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12
Q

What is the functional group, prefix and suffix of carboxylic acids?

A

> Functional group: -COOH
Prefix: Carboxy-
Suffix: -oic acid

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13
Q

What is the functional group and prefix of alkyls?

A

> Functional group: -CH3

> Prefix: Alkyl

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14
Q

What is the functional group, prefix and suffix of esters?

A

> Functional group: Carbon-oxygen double bond and carbon oxygen single.
Prefix: alkyl
Suffix: -oate

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15
Q

What is the functional group, prefix and suffix of aldehydes?

A

> Functional group: 2 alkyl groups connected to C and one double bond oxygen
Prefix: Oxo-
Suffix: -al

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16
Q

What is the functional group and prefix of haloalkanes?

A

> Functional group: -x (any halogen)

> Prefix: Halo-

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17
Q

Define general formula

A

Simplest algebraic formula for a homologous series

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18
Q

Define displayed formula

A

Show the relative positions of atoms and bonds

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19
Q

Define structural formula. E.g. Butane

A

Provides minimum detail for the arrangement of atoms. CH3CH2CH2CH3 OR CH3(CH2)2CH3

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20
Q

Define empirical formula

A

Shows the smallest whole-number ratio of atoms of elements in a compound.

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21
Q

Define molecular formula

A

Shows the number and types of atoms in a compound

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22
Q

Define skeletal formula

A

Simplified structural formula drawn by removing hydrogen from alkyl chains.

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23
Q

What are structural isomers?

A

Compounds with the same molecular formula but different structural formula.

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24
Q

What are the three structual isomers of C5H12?

A
  1. CH3CH2CH2CH2CH3
  2. CH3CH2CH(CH3)CH3
  3. CH3C(CH3)2CH3
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25
Q

What is stereoisomerism?

A

Compounds with the same molecular and structural formula but different arrangements of atoms in space

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26
Q

Describe E/Z isomerism

A

> Type of steroeisomerism

> Caused by restricted rotation around the double bond

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27
Q 
Why is the following an E isomer?
     Cl           H   
        \         /  
          C=C
        /         \ 
     H            CH3
A

As the highest priority (highest RFM) atoms are on opposite sides.

28
Q

What is the difference between saturated and unsaturated compounds?

A

Saturated compounds only contain single carbon-carbon bonds whereas unsaturated compounds have multiple carbon-carbon bonds

29
Q 
Why is the following an Z isomer?
     Cl           CH3
        \         /  
          C=C
        /         \ 
     H            H
A

As the highest priority (highest RFM) atoms are on same sides.

30
Q

What is cis/trans isomerism?

A

> Type of E/Z isomerism

> Where substituents are the same on each carbon atom

31
Q

Cis/Trans? E/Z?

     CH3       H   
        \         /  
          C=C
        /         \ 
     H            CH3
A

Trans - E

32
Q

Cis/Trans? E/Z?

     CH3       CH3  
        \         /  
          C=C
        /         \ 
     H            H
A

Cis - Z

33
Q

Describe homolytic fission

A

> When a covalent bond breaks and each electron goes to a different bonded atom.
Generate RADICALS - species with one or more unpaired electrons.

X–Y —> X• + Y•

34
Q

Describe heterolytic fission

A

> When a covalent bond breaks and both electrons goes to one of the bonded atoms.
Generates a cation and an anion.

X-Y –> X^+ + Y^-

35
Q

Describe the formation of a covalent bond

A

When two radicals or a cation and anion collide, a new bond is formed.

36
Q

How are alkanes saturated hydrocarbons?

A

As they only contain single covalent bonds.

37
Q

What is the general formula of alkanes?

A

CnH2n+2

38
Q

What is the bond angle and shape of alkanes? Why?

A

109.5° - Tetrahedral - due to electron pair repulsion.

39
Q

Describe the boiling points of alkanes

A

> Alkanes have induced dipole-dipole interactions (London forces) between the non-polar molecules
These get stronger as the molecules get larger due to increased POC between molecules
Therefore more energy is needed to overcome these forces as the molecules get larger.

40
Q

How does branching affect the boiling points of alkanes?

A

Alkanes with less branching have higher boiling points due to more POC which leads to stronger London forces therefore more energy is required.

41
Q

How reactive are alkanes?

A

Low reactivity

42
Q

Why do alkanes have a low reactivity?

A
  1. Covalent bonds in alkanes have higher bond enthalpies.

2. C–H sigma bonds have low polarities as the electronegativities of C and H are similar.

43
Q

What are the limitations of radical substitution in synthesis?

A
  1. The final product may collide again with other radicals causing further substitutions.
  2. Also, reaction may occur at different positions in a carbon chain.
44
Q

How are alkenes unsaturated hydrocarbons?

A

At least one C=C is present.

45
Q

What is the general formula of alkenes?

A

CnH2n

46
Q

What is the bond angles and the shape of alkenes?

A

120° - Trigonal planar

47
Q

Describe the reactivity of alkenes

A

> More reactive than alkanes
Due to low bond enthalpies of the pi bond
The pi bond is first to react and break whilst leaving the sigma bond behind.

48
Q

Define electrophile

A

Electron pair acceptor

49
Q

What is a primary carbocation?

A

H
|
R–C–H - One alkyl group
+

50
Q

What is a secondary carbocation?

A

R
|
R–C–H - Two alkyl groups
+

51
Q

What is a tertiary carbocation?

A

R
|
R–C–R - Three alkyl groups
+

52
Q

What is the order stability of primary to tertiary carbocations?

A
  1. Tertiary (Most)
  2. Secondary
  3. Primary (Least)
53
Q

What is the difference between a major and minor product?

A

Major products are more stable as they are usually consist of a secondary or tertiary carbocation intermediate whereas minor products consist of a primary carbocation intermediate.

54
Q

What does Markovnikov’s rule state?

A

That when H–X is added to an unsymmetrical alkene, the hydrogen attaches to the carbon with the most hydrogen atoms to start with. This is because carbocations that have alkyl groups attached are more stable than those with the hydrogen atoms attached.

55
Q

What is one advantage and disadvantage of dealing with polymer waste by combustion?

A

> Advantage: High calorific value

> Disadvantage: Toxic gases

56
Q

How is polymer waste dealt with by using landfills? What is a problem?

A

> Large holes are dug and the polymers are buried

> Many plastics are biodegradable so it remains for a long time.

57
Q

How is polymer waste dealt with by recycling? What is a problem?

A

> Plastics are sorted first
Then they are melted and reshaped
There are concerns that the quality of plastics are affected.

58
Q

How is polymer waste dealt with by organic feedstock?

A

> Series of chemical reactions can be used to break the plastic polymers into smaller organic molecules.
This allows recovered chemicals to be used in other industrial reactions.

59
Q

Describe biodegradable plastics

A

> Plastics that can be broken down chemically into harmless/useful substances
Substances such as plant starch is mixed with an addition polymer and the starch breaks over time.
However, there are still concerns that these small pieces still affect the environment.

60
Q

Describe photodegradable plastics

A

> Plastics that can be broken down chemically using energy with wavelengths similar to light.
Once the polymer is exposed, the process begins and it can’t be stopped.
However, photodegradable plastics in landfills may not receive sufficient light to break down.

61
Q

What is a radical?

A

Species with an unwanted electron

62
Q

What is a ‘curly arrow’?

A

Shows the movement of an electron pair, showing either heterolytic fission or the formation of a covalent bond.

63
Q

What are the 4 rules of nomenclature?

A
  1. Find the longest carbon chain as the main root name.
  2. Identify the most important functional group - gives the suffix e.g. -OH –> -OC.
  3. Identify ‘carbon numbers’ - priority to functional group and count from the end that will give the lowest numbers
  4. Pick out all other groups, order prefixes in alphabetical order - e.g. dichloro- is C not D.
64
Q

Describe the bonding of alkanes in terms of types of bonds.

A

> Carbon form four covalent bonds with other atoms
Each covalent bond has a direct overlap of electron clouds from each atom making a sigma bond.
Therefore C-C and C-H bonds are examples of sigma bonds.
Alkanes therefore have a free rotation around the sigma bonds allowing for a 3D tetrahedral shape.

65
Q

Describe the bonding of alkenes in terms of types of bonds.

A

> A sigma bonds are formed between two carbon atoms using the direct overlap of the electron clouds of the two atoms
The pi bond is formed by the electrons in the adjacent p-orbitals overlapping above and below the carbon atoms. Only made after sigma bond is made.
Alkenes therefore have a restricted rotation around the double bond meaning they can only have a ‘planar’ shape.

a level chemistry (7 decks)

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