4.1- basic Concepts And Hydrocarbons

Question 1

What is the functional group of aldehydes and ketones?

Answer 1

-CHO
-C-CO-C

Question 2

What is a homologous series?

Answer 2

Families of compounds with a common general formula containing the same functional group, similar properties and molecular formula differing by CH2

Question 3

What is an aromatic compound?

Answer 3

Aromatic compounds contain a benzene ring

Question 4

What is an aliphatic compound

Answer 4

A compound containing hydrogen and Carbon joined together in straight/branched chains and non aromatic rings

Question 5

What is alicyclic compound

Answer 5

An aliphatic compound arranged in. Non aromatic rings with/ without side chains

Question 6

What are rules regarding nomenclature of organic compounds

Answer 6

• when there’s multiple groups, list the groups alphabetically, then add the numbers e.g 3-Butlyl, 5- Ethyloctanoic acid
• for multiple of the same group on a compound, give a number indication of which C atom each group is on
  (E.g Di Tri Tetra)
• for alkenes C=C is always given the smallest number
• Cyclic compounds- cyclostemsuffix
• Note that for carboxylic acids and aldehydes are always numbered from the functional group as they have the highest priority and so don’t need a number

Question 7

What is a displayed formula?

Answer 7

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

Question 8

What is a Structural formulae

Answer 8

Shows the minimum detail for the arrangement of atoms in the molecule. Brackets are used to aid clarity for groups attached to C atoms

Question 9

What is skeletal formulae

Answer 9

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

Question 10

What is a functional group

Answer 10

A group of atoms responsible for the characteristic chemical reactions of a compounds

Question 11

What is a saturated hydrocarbon

Answer 11

Only have single bonds

Question 12

What is a general formula?

Answer 12

The simplest algebraic formula for a homologous series

Question 13

What is the empirical formula

Answer 13

Shows the smallest whole number ratio of atoms of the elements In compounds

Question 14

What is a molecular formula

Answer 14

Shows the numbers and types of atoms in a compound

Question 15

What is an unsaturated hydrocarbon

Answer 15

Organic compounds that contain only carbon an hydrogen, that have at least 1 C=C double bond

Question 16

What is an isomer?

Answer 16

Have the same molecular formula but different arrangements of their atoms

Question 17

What is a structural isomer?

Answer 17

Structural isomers are compounds with he same molecular formula but different structural formula

Question 18

What is functional group isomerism

Answer 18

Where the functional group is moved to a different position

Question 19

What is an E/Z isomer

Answer 19

E/Z isomerism is a type of stereoisomerism caused by the restricted rotation around the double bond- 2 different groups are are attached to both carbon atoms of the C=C double bond

Question 20

What is stereoisomerism

Answer 20

Organic compounds with the same molecular and structural formula but having different arrangements of atoms in space

Question 21

Why is the C=C double bond important in E/Z isomerism?

Answer 21

You can rotate single bonds, whereas the double bond would have to break and reform instead of rotate

Question 22

What determines whether an isomer is E or Z?

Answer 22

If the groups are in the same side of the alkene , it is a Z isomer
If the groups are on opposite sides of the alkene it is an E isomer

Question 23

What is Cis trans isomerism?

Answer 23

A type of E/Z isomerism which the 2 substituent groups attached to the C=C are the same

Question 24

What are the cahn ingold prelog rules?

Answer 24

A higher Mr gives a higher priority
If the highest priority groups are on the same side of the C=C, the isomer is Z. If on opposite sides, the isomer is E

Question 25

What is an alkane?

Answer 25

A homologous series of saturated hydrocarbons

Question 26

What bonds are formed by alkanes?

Answer 26

Each C atom can form up to 4 covalent bonds Each covalent bond has a direct overlap of electron clouds from each atom, forming a sigma bond eg C-C and C-H are both examples

Question 27

What is the shape and bond angle of alkanes?

Answer 27

Tetrahedral 109.5

Question 28

Alkanes are non polar. Why?

Answer 28

The electronegativity of C 2.55 and H 2.20 are very similar ( not large difference in electronegativity) so alkanes are non polar and display London forces only

Question 29

Explain how length of alkane chain affects boiling point

Answer 29

The longer the alkane chain, the higher the boiling point, the larger molecules have more surface area contacts between adjacent molecules, increasing the amount of instantaneous dipoles (London forces) created. more energy is needed to overcome the intermolecular attractions

Question 30

Explain why structural isomers of alkanes that display different levels of branching have different boiling points

Answer 30

The more branched a compound, the fewer Surface area interactions there are between molecules as molecules cannot pack as closely together,giveing fewer points of contact. Fewer London forces and so less energy required to overcome intermolecular forces

Question 31

What reactions do alkanes undergo?

Answer 31

Combustion Radical substitution

Question 32

What is complete combustion? Give a general formula for the complete combustion of alkanes

Answer 32

Oxidising fuel in a plentiful supply of air CnH2n+2 + (3n+1)/2 O2 —> nCO2 + (n+1)H2O

Question 33

What is incomplete combustion? Give 2 general formulas for incomplete combustion of alkanes

Answer 33

Oxidising fuel in a limited supply of air CnH2n+2 + (2n+1)/2 O2 —> nCO + n+1H2O CnH2n+2 + (n+1)/2 O2 —> nC + (n+1) H2O

Question 34

What are the 3 steps of radical substitution/ alkane halogenation?

Answer 34

1) initiation- UV light or heating provided energy to break the halogen-halogen bond in some of the molecules, forming radicals 2) Propagation- 2 repeated steps forming a chain reaction where are radical and reactant give a product and a new radical. Builds up the desired product 3) Termination- 2 radicals react/ collide to form a stable product

Question 35

What is a reaction mechanism?

Answer 35

A model showing the sequence of steps that show the movement of electrons during a reaction

Question 36

What do curly arrows represent?

Answer 36

The flow of electron pairs during reaction mechanisms

Question 37

What is homolytic fission?

Answer 37

The breaking of a covalent bond where each bonding atom receives an me electron from the bonded pair, forming 2 radicals

Question 38

What is heterolytic fission?

Answer 38

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

Question 39

What is a radical?

Answer 39

A species with 1+ unpaired electrons