3.3 Organic Chemistry: .1 Introduction to organic chemistry

Question 1

what is the empirical formula?

Answer 1

the simplest ratio of atoms of each element in a compound

Question 2

what is the molecular formula?

Answer 2

the actual number of atoms of each element in a molecule

Question 3

what does the structural formula show you?

Answer 3

shows the atoms carbon by carbon with the attached hydrogens and fucntional group

e.g CH₃CH₂CH₂CH₂OH

Question 4

what is the skeletal formula?

Answer 4

• shows the bonds of the carbon only with any functional groups
• the hydrogen and carbon atoms arent shown

Question 5

what is the displayed formula?

Answer 5

shows how all atoms are arranged, and all the bonds betweent them

Question 6

what is a homologous series?

Answer 6

a group of compounds that contain the same functional group.

-they can all be represented by the same general formula

Question 7

what are the features of a homologous series?

Answer 7

• they have the same functional group
• they react in a similar way
• they have the same general molecular formula

Question 8

what is nomenclature

Answer 8

the naming of organic compounds

Question 9

what the rules for nomenclature

Answer 9

1. count the carbons in the longest continous chain that contains the fucntional group, this gives you the stem
   e. g No. of carbon: 1 (meth-), 2(eth-), 3(prop-), -5(pent-), 6(hex-)
2. the main functional group of the molecule usually gives you the end of the name (the suffix)
   e. g -ane (alkenes) OR -ene (alkenes) OR -ol (acohols)
3. Number the carbons in the longest carbon chain so that the carbon with the main functional group attached has the lowest possible number. If there is more than one longest chain, pick the one with the one with the most side chains.
4. write the carbon number that the fucntional group is on before the suffix aded as prefixes at the start of the name. Put them in alphabetical order,with the number of carbon atom each is

5.) any side chains or less important functional groups are

attached to

6.) if there is more than one identical side-chain or fucntional group, use di- (2), tri-(3) or tetra-(4) before that part of the name

Question 10

for each side group state what the prefix is

CH3

CH2CH2

F

Cl

Br

I

Answer 10

CH3- methyl

CH2CH2- ethyl

F- fluoro

Cl- chloro

Br- bromo

I- iodo

Question 11

what is the IUPAC system?

what is the benfit of this system?

Answer 11

• it is the agreed international language of chemsitry
• the IUPAC system means that scientific ideas can be communicated across the globe more effectively. So its easier for scientists to get on with testing each other’s work, and either comfirm or dispute new theories.

Question 12

draw the structural, displayed and skeletal formula of cyclohexane

Answer 12

-structural: CH2CH2CH2CH2CH2CH2

Question 13

what is the IPUAC name for this chemical?

Answer 13

2-methylpentane

Question 14

answer these summary questions on nomenclature

Answer 14

answers

Question 15

draw the structure of 2-methylpentane

Answer 15

Question 16

what is a mechanism?

Answer 16

• what is a mechanism is a diagram that breaks reacttion down into individual stages.
• they show how molecules react together by using curly arrows to show which bonds are made or broken

Question 17

what does a curly arrow show?

Answer 17

electron movement

-goes from lone pair of electron to where a new bond is formed at the end of the reaction

Question 18

what is the free radical susbstituion reaction when halogens react with organic compounds

Answer 18

this is where halogen react with alkanes in photochemical reaction- reactions that are started by ultraviolet light

-a hydrogen atom is substituted by chlorine or bromine

Question 19

how is a free radical formed?

Answer 19

it is formed when a covalent bond breaks by homolytic fission (equal spitting of a bond) to form a particle with an unpaire electron

Question 20

In the reaction of chlorine reacting with methane to form:

CH₄ + Cl₂ -^UV-> CH₃Cl + HCl

describe the initiation reaction and give a eqation to represent this

Answer 20

• sunlight provides enough energy to break the Cl-Cl bond (this is called photodissociation)
• the bond splits eqaully and each atom gets to keep one electron, the atom becomes a highly reactive free radical because of its unpaired electron

Cl₂ –^UV–> 2Cl•

Question 21

In the reaction of chlorine reacting with methane to form:

CH4 + Cl2 -UV-> CH3Cl + HCl

describe the 1st propogation reaction and give a eqation to represent this

Answer 21

• in the first propogation step the HALOGEN RADICAL with the ALKANE
• the halogen radical ALWAYS TAKES A HYDROGEN
• a HYDROGEN HALIDE and ORGANIC COMPOUND RADICAL is made
• Cl• + CH4 –> HCl + CH₃• (better if the radical is on top of Carbon)

Question 22

In the reaction of chlorine reacting with methane to form:

CH4 + Cl2 -^UV-> CH3Cl + HCl

describe the 2nd propogation reaction and give a eqation to represent this

Answer 22

• in the second propogation step, the new ORGANIC COMPOUND RADICAL always reacts with the HALOGEN
• the halogen-halogen (e.g Cl-Cl) bond breaks by homolytic fission
• a HALOGENALKANE and a Halogen radical is made

CH₃• + Cl₂ –> CH₃Cl + Cl•

Question 23

In the reaction of chlorine reacting with methane to form:

CH4 + Cl2 -UV-> CH3Cl + HCl

describe the termination reaction and give a eqation to represent this

Answer 23

• in the termination step the free radicals combine
• there will ALWAYS be only THREE reactions possible:

HALOGEN radical and HALOGEN radical reacting together

Cl• + Cl• –> Cl₂

ORGANIC COMPOUND radical and ORGANIC COMPOUND radical

CH₃• + CH₃ •–> CH₃CH₃

ORGANIC COMPOUND radical and HALOGEN radical

CH₃• + Cl• –> CH₃Cl

Question 24

if the chlorine’s is in excess in the free radical substitution of methane and chlorine produce equations for the further reactions.

state which substituions they would occur at (e.g 2nd, 3rd, 4th)

Answer 24

(this is you first reaction) 1st sub: CH4 + Cl2 –> CH3Cl + HCl

2rd sub: CH3Cl + Cl2 –> CH2Cl2 + HCl

3th: CH2Cl2 + Cl2 –> CHCl3 + HCl
4th: CHCl3 + Cl2 –> CCl4 + HCl

Question 25

what is the disadvantage of free radical substitution?

Answer 25

-a mixture of products and the desired product would have to be seperated from the other products

Question 26

what is meant by structural isomerism?

Answer 26

this is when chemicals have the same molecular formula but different structural formulae

Question 27

what are the 3 types of structural isomers?

Answer 27

- chain - positional - functional group

Question 28

what is the difference between chain isomers?

Answer 28

they have different chain lenghts (the carbon chain may go from 4 -bute to 3 -prop)

Question 29

what is the difference between positional isomers?

Answer 29

- the functional group or side group in poisitional isomers change position e. g

Question 30

what is the difference in functional group isomers?

Answer 30

-the difference between functional group isomers is that they have different functional group. Which means they have different homologous series

Question 31

what are the two types of different stereoisomerism isomers (geometric isomers)

Answer 31

E-Z isomers

Question 32

what is stereoisomerism (geometric isomers)?

Answer 32

this is where two (or more) compounds have the same structural formula but they differ in the arrangment of the bonds in space

Question 33

what type of compounds do you find E-Z isomers in?

Answer 33

alkenes

Question 34

describe what a z isomer looks like draw the z-isomer of but-2-ene (what is the name of this molecule?)

Answer 34

the z-isomer has the same groups either both above or both below the double bond this molecule is Z-but-2-ene

Question 35

describe what an e isomer looks like draw the e-isomer of but-2-ene (what is the name of this molecule?)

Answer 35

the e-isomer has the same groups positioned across the double bond this molecule is called E-but-2-ene

Question 36

way of remembering e-z isomers

Answer 36

- E stands for 'entgegen' which in german means opposite - Z stands for 'zusammen' which in german means together so -you can remember the z-isomer: the 'ze zame zide' -you can remember the e-isomer: they are 'enemies'

Question 37

draw the e-isomer of hex-3-ene

Answer 37

\*make sure that you put the CH3 at the end of your chain so that the carbons are only making 4 chains

Question 38

draw the z-isomer of hex-3-ene

Answer 38

\*make sure that you put the CH3 at the end of your chain so that the carbons are only making 4 chains

Question 39

what is the Cahn-Ingold-Prelog Rules (CIP)?

Answer 39

- when all of the groups coming off the double bond are different, you look for the heaviest element/molecule (in terms of RAM/RMM) coming off the carbon - if the two heaviest ones are on the same side of the double bond the compund is the z-isomer - if the two heaviest ones on the oposite sides of the double bond the compound is the e-isomer