module 4: core organic chemistry Flashcards

1
Q

what are structural isomers?

A

compounds with the same molecular formula but different structural formulae

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2
Q

what is a hydrocarbon?

A

a compound that contains only hydrogen and carbon

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3
Q

what does saturated mean?

A

containing single bonds only

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4
Q

what does unsaturated mean?

A

containing a double carbon-carbon bond

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5
Q

what is a skeletal formula?

A

a simplified organic formula

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6
Q

what is a homologous series?

A

a series of organic compounds with the same functional group (similar chemical properties) whose successive members differ by the addition of a -CH2- group

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7
Q

what is the general formula for alkanes?

A

CnH2n+2

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8
Q

what are alkanes?

A

saturated hydrocarbons

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9
Q

what are alkenes?

A

unsaturated hydrocarbons

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10
Q

what is a functional group?

A

the part of the organic molecule responsible for its chemical reactions

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11
Q

what are the products of the complete combustion of alkanes?

A

carbon dioxide + water

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12
Q

what are the products of the incomplete combustion of alkanes?

A

carbon monoxide (or carbon) + water

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13
Q

describe the reactions of alkanes with halogens

A
  • alkanes react with halogens, but only in the presence of sunlight
  • high energy UV radiation present in sunlight provides the initial energy for a reaction to take place
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14
Q

what type of reaction is that of alkanes with halogens?

A

a substitution reaction - a hydrogen atom in the alkane is substituted by a halogen atom

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15
Q

what are the three stages that make up the mechanism of the bromination of alkanes?

A

step 1 = initiation
step 2 = propagation
step 3 = termination

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16
Q

describe what happens in the first stage of the bromination of alkanes

A

stage 1 = initiation
- the reaction is started when the covalent bond in a bromine molecule is broken down by homolytic fission
- each bromine atom takes one electron from the pair, forming two highly reactive bromine radicals
- energy for this bond fission is provided by UV radiation

Br - Br –> Br* + Br*

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17
Q

what is a radical?

A

a very reactive species with an unpaired electron

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18
Q

describe what happens in the second stage of the bromination of alkanes

A

stage 2 = propagation
- the reaction propagates through two propagation steps, a chain reaction

Propagation step 1: CH₄ + Br* –> ·CH3 + HBr
Propagation step 2: ·CH3 + Br2 –> CH3Br + Br*

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19
Q

what happens in the first propagation step?

A

a bromine radical reacts with a C - H bond in the methane, forming a methyl radical and a molecule of hydrogen bromide

20
Q

what happens in the second propagation step?

A

each methyl radical reacts with another bromine molecule, forming bromomethane and a new bromine radical

21
Q

describe what happens in the third stage of the bromination of alkanes

A
  • two radicals collide, forming a molecule with all electrons paired
  • there are a number of possibilities
  • when two radicals collide and react, both radicals are removed from the reaction mixture, stopping the reaction
22
Q

what can hydrocarbons be classified as?

A
  • aliphatic
  • aromatic
  • alicyclic
23
Q

what are aliphatic hydrocarbons?

A

carbon atoms are joined to each other in an unbranched (straight) or branched chains, or non-aromatic rings

24
Q

what are alicyclic hydrocarbons?

A

carbon atoms are joined to each other in ring (cyclic) structures, with or without branches

25
Q

what are aromatic hydrocarbons?

A

some or all of the carbon atoms are found in a benzene ring

26
Q

what is homolytic fission?

A

the breaking of a covalent bond where each of the bonded atoms take one of the shared pair of electrons from the bond

27
Q

what is heterolytic fission?

A

the breaking of a covalent bond where one of the bonded atoms takes both of the electrons from the bond

28
Q

what are the two types of bond fission?

A

homolytic and heterolytic fission

29
Q

in a reaction mechanism, what do curly arrows represent?

A

movement of electron pairs when bonds are being broken or made

30
Q

what is a sigma bond?

A

the direct overlap of two orbitals

31
Q

what is a pi bond?

A

the sideways overlap of two p-orbitals

32
Q

explain the effect of increasing chain length on the boiling points of alkanes

A
  • increased chain length
  • greater surface area of contact
  • stronger london forces
  • more energy required to overcome these forces
  • boiling point increases
33
Q

explain the effect of branching on the boiling points of alkanes

A
  • more branching
  • less surface area of contact
  • weaker london forces
  • less energy required to overcome these forces
  • boiling point decreases
34
Q

what is a nucleophile?

A

an electron pair donor

35
Q

what is an electrophile?

A

an electron pair acceptor

36
Q

state and explain how the rates of hydrolysis of the chloroalkane and the bromoalkane would differ

A
  • rate slower with the chloroalkane
  • C-Cl bond is stronger than C-Br bond
37
Q

what are the reagents and conditions for an alkene to alcohol reaction?

A

steam and acid catalyst

38
Q

what are the reagents and conditions for an alkane to haloalkane?

A

halogen and UV

39
Q

state what is meant by the term ionic bond

A

electrostatic attraction between positive and negative ions

40
Q

describe the use of aqueous barium chloride in qualitative analysis

A
  • test for sulfate ions
  • white precipitate forms
41
Q

describe the oxidation reactions of butan-1-ol forming an aldehyde and carboxylic acid

A

oxidation reaction forming an aldehyde:
- acidified potassium dichromate
- heat and distillation
- organic product is butanal

oxidation reaction forming a carboxylic acid:
- acidified potassium dichromate
- heat under reflux
- organic product is butanoic acid

42
Q

suggest the general formula for a carboxylic acid

A

CnH2n+1COOH

43
Q

what are the differences between pi and sigma bonds?

A
  • a sigma bond is between bonding atoms and a pi bond is above and below the bonding atoms
  • a sigma bond has direct overlap of orbitals and pi bond has sideways overlap of orbitals
  • pi bond has a lower bond enthalpy
  • sigma bond has electron density between bonding atoms and pi bond has electron density above and below bonding atoms
44
Q

what are the reagents for an alcohol to haloalkane reaction?

A

sodium halide and sulfuric acid

45
Q

what are the reagents for an alkene to haloalkane reaction?

A

hydrogen halide

46
Q

what are the reagents for an alcohol to alkene reaction?

A

concentrated sulfuric acid

47
Q

what are the reagents for an alkene to alkane reaction?

A

H₂ and nickel catalyst