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Chemistry Module 4 > Basic Concepts and Hydorcarbons > Flashcards

Basic Concepts and Hydorcarbons Flashcards

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1
Q

Why do we name organic compounds

A

scientists communicate in many different languages therefore it is important that each chemical substance has its own unique name, avoids ambiguity
the IUPAC developed a naming system for organic chemicals called nomenclature

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2
Q

what are the first 4 alkanes called

A

Methane
Ethane
Propane
Butane

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3
Q

What are the three rules for naming branched alkanes

A 
stem = the main part of the name generated by identifying the longest carbon chain or parent chain
suffix = the end of the name identifying the most important functional group 
prefix= the front part of the name identifying the other functional groups and the carbon atoms there attracted to
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4
Q

What happens when you remove an hydrogen atom from an alkane

A

an akyl group is formed

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5
Q

name the 10 alkyl groups and there formula

A 
methyl CH3
ethyl C2H5
propyl C3H7
butyl C4H9
pentyl C5H11
hexyl C6H13
heptyl C7H15
octyl C8H17
nonyl C9H19
decly C10H21
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6
Q

What is the prefix of an alcohol

A

Hydroxy

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7
Q

what is the suffix of a carboxylic acid

A

oic

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8
Q

what is the suffix and functional group of a ketone

A

one

c-co-c

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9
Q

what is the formula for alkanes

A

CnH2n+2

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10
Q

what is the formula for alkenes

A

CnH2n

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11
Q

what is the formula of alcohols

A

CnH2n+1OH

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12
Q

what are cyclic compounds

A

they are saturated hydrocarbons

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13
Q

what do aromatic compounds always have

A

6 carbon rings and the molecular formula C6H6

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14
Q

why are aromatic compounds more stable

A

they are stable as all electrons are shared out across all carbon atoms therefore they are rarely involved in a chemical reaction

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15
Q

in a carboxylic acid where is the double bond

A

between carbon atoms and oxygen atoms

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16
Q

What is covalent bond fission

A

this is during the first stage of a chemical reaction when the activation energy effects the covalent bond causing them to break this is describe as undergoing fission

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17
Q

When does homolytic fission occur

A

this occurs when a covalent bond breaks and each electron goes to a different bonded atom,
this generates two highly reactive neutral species called radicals,

18
Q

What do radicals have

A

they have one or more unpaired electrons which are shown as dots

19
Q

what does UV light do

A

causes the covalent bond to break as it breaks the weaker pie bonds then the sigma bonds

20
Q

When does heterolytic fission occur

A

this occurs when a covalent bond breaks and both electrons go to one of the bonded atom this results in a a positive ion and negative ion being formed

21
Q

What is covalent bond formation

A

this is when two radicals or two oppositely charged ions collide and a new bond is formed

22
Q

What are carboncations properties

A

very reactive intermediates as they are very unstable

23
Q

what do alkanes have

A
  • hydorcarbons containing only hydrogen and carbon atoms
  • saturated containing only single covalent bonds
  • have the general formula CnH2n+2
  • have a graduation in physical properties
  • have similar chemical properties
24
Q

What are the bonding in alkanes

A

tetrahedral shape with a bond angle of 109.5, 4 bonding pairs

25
Q

What are alkanes a example of in terms of bonding

A

they are an example of sigma bonds, each covalent bond has a direct overlap of electron clouds between each atom making a sigma bond

26
Q

Describe the boiling points of alkanes

A
  • as chain length increases the relative molecular mass increases,
  • large molecules have more surface area contact with adjacent molecules this increases the number of induced dipole-dipole forces therefore more energy is needed to overcome the intermolecular attraction in order to break the chain therefore boiling points increase
27
Q

What do chains do to the boiling point of alkanes

A

the more branched a compound is the fewer surface area interactions there are between adjacent moleucles as they cannot fit together neatly, therefore branched molecules have fewer dipole dipole attractions and less energy is needed to break the intermolecular attraction and the boiling point decreases
- reduces ability of molecules to pack closely together

28
Q

Why do alkanes have low reactivity

A
  • all the covalent bonds in alkane molecules have high bond enthalpies therefore a large amount of energy is needed to break the bonds
  • the carbon-hydrogen sigma bonds have a very low polarity because of the electronegativity’s of carbon and hydrogen are almost the same
29
Q

What is combustion

A

Combustion is a rapid oxidation reaction which combines oxygen from the air with another substance

30
Q

What is complete combustion

A

this happens when there is a plentiful of air therefore enough oxygen to undergo complete combustion

  • makes clean blue flame and transfers the maximum amount of thermal energy because it fully oxidises carbon and hydrogen
  • produces water and carbon dioxide
31
Q

what is incomplete combustion

A

this is when there is not enough oxygen to react completely with the alkane
- produces water and carbon monoxide this can be dangerous

32
Q

complete combustion equation

A

CnH2n+2 + (3n+1/2)02 = nCO2 + (n+1)H20

33
Q

incomplete combustion equation

A

CnH2n+2 + (n+0.5)02 = (n+1)H20 + nCO

34
Q

What do alkanes react with to from halogenated organic compounds (Halogenation)

A

they react with bromine and chlorine in the presence of UV light,

35
Q

How does halogenation works and what happens in it

A

Happens by homolytic fission of the halogen molecules which form radicals
- A hydrogen atom in the alkane is substituted by a halogen atom, if the reaction conditions are maintained the substitutions can continue until all the hydrogen atoms in the original alkane have been replaced by halogen atoms

36
Q

what is the three stages of radical substitution mechanism

A
  • initiation
  • propagation
  • termination
37
Q

Disadvantages of radical substitution

A
  • unpredictable
  • difficult to control
  • mixture of products is formed which has to be separate by processes of fractional distillation of chromatography
  • radicals are highly reactive
  • multiple substitutions
38
Q

Describe steps of radical substitution

A
  • initiation - UV light breaks the covalent bond by heating it a radical has been generated
  • propagation - radical reacts with the alkane and produces an alkyl radical and hydrogenradcial, the the desired product is created from the alkyl radical and orginal cl2 or br2, regenerates the chlorine radical
  • termination -radicals react with each other forming other elements and the product itself
39
Q

Why does radical substitutions chain reactions

A

because the radicals keep getting produced and used

40
Q

how is the carboxyl group and ester group represented in structural formulae

A

COOH

COO

41
Q

Draw radical subsitiution steps for chlorine and bromine

A

DRAW IT

42
Q

what does aliphatic mean

A
  • this is a molecule that is made up of hydrogen atoms and carbon atoms which may contain rings and branches but is not aromatic

Chemistry Module 4 (8 decks)

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