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Chemistry > AS Organic Chemistry > Flashcards

AS Organic Chemistry Flashcards

0
Q

What is a radical?

A

A species with an unpaired electron

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1
Q

What is homolyitic fission?

A

The breaking of a covalent bond, with one of the bonded electrons going to each atom, forming two radicals

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2
Q

What is heterolytic fission?

A

The breaking of a covalent bond with both of the bonded electrons going to one of the atoms, forming a cation (+ ion) and an anion (- ion)

The two species are different

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3
Q

What is a nucleophile?

A

An atom (or group if atoms) that is attracted to an electron-deficient centre or atom, where it donates a pair of electrons to form a new covalent bond

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4
Q

What is an electrophile?

A

An atom (or group of atoms) that is attracted to an electron-rich centre or atom, where it accepts a pair of electrons to form a covalent bond

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5
Q

What is an addition reaction?

A

A reaction where a reactant is added to an unsaturated molecule to make a saturated molecule

2 reactants —> 1 product

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6
Q

What is a substitution reaction?

A

A reaction in which an atom or group of atoms is replaced by a different atom or group atoms

2 reactants —> 2 products

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7
Q

What are structural isomers?

A

Molecules with the same molecular formula, but with different structural arrangement of atoms

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8
Q

What are stereoisomers?

A

Compounds with the same structural formula, but with a different arrangement of the atoms in space

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9
Q

What is E/Z isomerism?

A

A type of stereoisomerism in which different groups attached to each carbon of a C=C bond may be arranged differently in space because of the restricted rotation of the C=C bond

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10
Q

What is cis-trans isomerism?

A

A special type of E/Z isomerism, in which the is a non-hydrogen group and hydrogen on each C of a C=C double bond.

The cis isomer(Z isomer) has H atoms on each carbon on the same side.

The trans isomer (E isomer) has H atoms on each carbon on different sides

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11
Q

What does structural formula show?

A

The minimal detail for the arrangement of atoms in a molecule.

i.e. Bropane —> CH3CH2CH3
1-Bromopropane —> CH3CH2CH2Br

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12
Q

What is skeletal formula?

A

A simplified organic formula, with H atoms removed from alkyl chains, leaving just a carbon skeleton and associated functional groups

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13
Q

Amount (n) =

A

mass (m)
—————————
molar mass (N)

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14
Q

What is general formula?

A

The simplest algebraic formula of a member of a homologous series

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15
Q

What does displayed formula show?

A

The relative positioning of all the atoms in a molecule and the bonds between them

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16
Q

What is a functional group?

A

The part of the organic molecule responsible for its chemical reactions

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17
Q

What is a homologous series?

A

A series of organic co pounds with the same functional group, but with each successive member differing by CH2

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18
Q

What are alkanes?

A

The homologous series with the general formula CnHn+2

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19
Q

What’s the effect of chain length on the boiling points of alkanes?

A

As the chain length increases there are more points of contact, leading to more van der Waals’ forces between the molecules.

This means it takes more energy, and therefore a higher temperature to separate longer molecules.

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20
Q

What is the effect of branching on the boiling points of alkanes?

A

Branched molecules have fewer pints of contact and are further apart than I branched molecules so there are fewer intermolecular forces.

Therefore, leases energy (heat) is required to separate the molecules

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21
Q

What is cracking?

A

The breaking down of long-chained saturated hydrocarbons to form shorter-chained alkanes and alkenes.

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22
Q

What is a catalyst?

A

A substance that increases that the rate of a chemical reaction without being used up in the process

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23
Q

What is crude oil?

A

Crude oil is a mxiture of hydrocarbons. It is also known as petroleum.

It is made of of mainly alkanes, with some alkenes and other hydrocarbons. They range from 1 carbon chains of methane to 50 carbon chains of Pentacontane.

Crude oil is not at all useful as a mixture, but when separated it is extremely useful. The process of breaking up crude oil is called fractional distillation.

24
Q

What is fractional distillation?

A

This is the process of breaking up crude oil.

Crude oil is placed in a fractionating column. The crude oil is heated and as it rises through the column it gets cooler, so different fractions cool and condense.

The largest carbon chains do not vaporise at all - so they form a thick sticky residue at the bottom of the column. This contains substances like bitumen for roads and roofs.

25
Q

What is thermal cracking?

A

Cracking that takes places at high temperature (up to 1000ºC) and high pressure (up to 70 atm).

It produces lots of alkenes and these alkenes are used to make very valuable products, like polymers. A good example is poly(ethene), which is made from ethene.

26
Q

What is catalytic cracking?

A

Cracking that uses a catalyst.

This makes mostly motor fuels and aromatic hydrocarbons.

It uses something called a zeolite catalyst, at a slight pressure and high temperature (about 450ºC).

Using a catalyst cuts costs, because the reaction can be done at lower temperature and pressure. The catalyst also speeds up the reaction, and time is money.

27
Q

Why can carbon forms so many compounds?

A

Because:

  • A carbon atom can form bonds with other carbon atoms to form chains and rings
  • A carbon atom can form single, double, or triple bonds to another carbon atom
  • a carbon atom can bond to atoms of other elements
28
Q

Define an aliphatic hydrocarbon

A

A hydrocarbon where the carbon atoms are joined together in straight unbranched or branched chains

29
Q

Define an alicyclic hydrocarbon

A

A hydrocarbon where the carbon atoms are joined together in a ring structure

30
Q

What is an elimination reaction?

A

A reaction where one reactant reacts to form two products

A molecule is removed from a saturated molecule to form an unsaturated molecule

31
Q

Define percentage yield

A

A measure of the proportion of products formed in a reaction

32
Q

Define atom economy

A

A measure of the proportion of the products that are used

33
Q

How are pure liquid obtained from crude oil?

A

By th further distillation of a crude oil fraction

34
Q

After combustion, there will always be:

A
  • The same number of CO2 molecules as carbon atoms

- Half the number of H2O molecules as hydrogen atoms

35
Q

Why are short chained hydrocarbons in high demand?

A
  • Short chained alkanes for use as fuels

- Short chained alkenes for use for polymer production

36
Q

In cracking how are long chained alkanes broken down

A

Randomly

37
Q

How are branched alkanes formed from unbranched alkanes?

A

Isomerisation

38
Q

How are aliphatic hydrocarbons converted into cyclic hydrocarbons?

A

Reforming

39
Q

Why are branched and cyclic alkanes are important for petrol?

A

They are petrol additives which promote more efficient combustion than straight-chain alkanes

40
Q

How is the hydrogen produced in reforming used?

A

Ammonia production and margarine production

41
Q

Define empirical formula

A

The simplest, whole-number ratio of elements in a compound

42
Q

Define molecular formula

A

The actual number of atoms of each element in a molecule

43
Q

Why, when studying reactions of a homologous series, why is the alkyl group relatively unimportant?

A

It is the functional group that reacts

44
Q

Percentage yield =

A

(Actual yield / theoretical yield ) x 100

45
Q

Atom economy =

A

Molecular mass of desired product
—————————————————- X 100
Sum of molecular masses of all products

46
Q

Why do different alkanes have different melting and boiling points?

A

Boiling points increase with increasing chain lengths because of the increasing strength of intermolecular forces

For hydrocarbons of similar molecular mass, branched alkanes have lower boiling points because there are fewer interactions possible between molecules

47
Q

What are the stages of radical substitution?

A

Initiation, propagation, termination

48
Q

Describe initiation

A

Ultraviolet radiation provides energy to break Cl–Cl bonds homolytically producing chlorine radicals

49
Q

Describe propagation

A

The reaction products are made

Radicals are recycled in a chain reaction

50
Q

Describe termination

A

Radicals react together and are removed from the reaction mixture

51
Q

In mechanisms, a curly arrow is used to show the movement of a pair of electrons.

The movement of the electron pair involves either:

A
  • The formation of a new covalent bond or
  • The heterolytic fission of a covalent bond

The curly arrow always goes from and electron pair or double bond

52
Q

Reduction of an organic compounds involves what?

A

Loss of oxygen or gain of hydrogen (accompanied by a gain of electrons)

53
Q

The process of adding hydrogen across a double bond is sometimes referred to as ____________

A

Hydrogenation

54
Q

A hydrolysis reaction is?

A

A reaction in which water breaks a bond

55
Q

What is the catalyst used in catalytic cracking?

A

Zeolite catalyst

56
Q

Write an equation to show the complete combustion of ethanol under standard conditions

A

C2H5OH(l) + 3O2(g) —> 2CO2(g) + 3H2O(l)

57
Q

Explain, using bond energies, why combustion is exothermic

A

More heat energy is released on forming the stronger bonds in the products than is taken in to break the bonds in the reactants

Chemistry (7 decks)

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