Alkanes

Question 1

What is the general formula of alkanes?

Answer 1

CnH2n+2

Question 2

What is the shape around every carbon atom?

Answer 2

Tetrahedral

109 degrees

Question 3

What are the 2 conformations of alkanes?

Answer 3

Eclipsed

Staggered

Question 4

Which of the 2 conformations of alkanes are more stable?

Answer 4

Staggered as there is maximum separation

Question 5

What are the 2 types of isomers?

Answer 5

Structural

Stereo/geometric

Question 6

What are the 3 types of structural isomers?

Answer 6

Branched
Functional group
Branched

Question 7

What are the 3 types of stereo isomers?

Answer 7

E/Z
Cis/Trans
Optical

Question 8

Definition of structural isomers

Answer 8

Same molecular formula but different structural formula

Question 9

What are branched isomers?

Answer 9

Branch it (same number of Cs)

Question 10

What are functional group isomers?

Answer 10

Change functional group

Eg alcohol-ester

Question 11

What are positional isomers?

Answer 11

Change position of functional group

Question 12

What is heterolytic bond fission?

Answer 12

Makes positive and negative ions

Pair of electrons in covalent bond go to one of the atoms that is bonded

Question 13

What does a curly arrow show?

Answer 13

Movement of a pair of electrons

Question 14

What is homolytic bond fission?

Answer 14

Makes radicals

1 electron in pair of electrons goes to each atom in covalent bond

Question 15

What are radicals?

Answer 15

Species with an unpaired electron that are very reactive

Question 16

What do fish hooks/half arrows show?

Answer 16

The movement of 1 electron

Question 17

What are the three types of reactions for alkanes?

Answer 17

Elimination
Substitution
Addition

Question 18

What are the 2 types of covalent bond?

Answer 18

Sigma (single)

Pi (double)

Question 19

What are stronger sigma or Pi bonds?

Answer 19

Sigma

Question 20

Definition of sigma bonds

Answer 20

End on overlap of orbitals on the line directly between bonded atoms.

Question 21

What forces are between alkanes?

Answer 21

LDF

Question 22

What 2 things affect the boiling point of alkanes?

Answer 22

Number of electrons (mainly)

Surface area of contact (if same number of e-)

Question 23

When comparing boiling points, what do you say if one has more electrons?

Answer 23

More electrons so larger instantaneous/ induced dipoles so stronger LDF so more energy needed to break forces so higher boiling point.

Question 24

When comparing boiling points, what do you say if they have the same number of electrons but 1 is branched?

Answer 24

Same number of electrons however X does’t have branches so there is a larger surface area of contact so stronger LDF so more energy needed to break forces so higher boiling point.

Question 25

How many alkanes are gases at room temperature?

Answer 25

The first 4

Question 26

What is produced in complete combustion?

Answer 26

Carbon dioxide (g) and water (l)

Question 27

What is produced in incomplete combustion (normally)

Answer 27

Carbon monoxide (g) and water (l)

Question 28

What is produced in incomplete combustion (when a solid is produced)

Answer 28

Carbon (s) and water (l)

Question 29

What is produced when an alkane reacts with a halogen?

Answer 29

Haloalkane + hydrogen halide

Question 30

What is the mechanism called when an alkane reacts with a halogen?

Answer 30

Free radical substitution

Question 31

What are the condition is needed in free radical substitution?

Answer 31

UV light

Question 32

What are the 4 steps to a free radical substitution answer?

Answer 32

Overall equation Initiation Propagation Termination

Question 33

What happens in initiation (free radical substitution)

Answer 33

Radicals are made | Remember to say homolytic bond fission!

Question 34

What happens in propagation step 1? (free radical substitution)

Answer 34

Organic+radical goes to (Organic-H radical) and hydrogen halide

Question 35

What happens in propagation step 2? (free radical substitution)

Answer 35

(Organic-H radical)+halogen goes to haloalkane and radical

Question 36

What happens in termination? (free radical substitution

Answer 36

Radicals combine

Question 37

What is the first problem with free radical substitution?

Answer 37

Can get substitution at different positions

Question 38

What is the seconds problem with free radical substitution?

Answer 38

Can get more substitutions than wanted

Question 39

How do you limit more substitutions occurring in free radical substitution?

Answer 39

Have excess of the organic substance so radicals always react with that instead of products that are made in the reaction.

Question 40

What is added in free radical when you want 2 Hs to be substituted?

Answer 40

2CL2/2Br2/2I2 | 2 halogen halides are also made