3.3 Organic Chemistry: .1 Introduction to organic chemistry Flashcards
what is the empirical formula?
the simplest ratio of atoms of each element in a compound
what is the molecular formula?
the actual number of atoms of each element in a molecule
what does the structural formula show you?
shows the atoms carbon by carbon with the attached hydrogens and fucntional group
e.g CH3CH2CH2CH2OH
what is the skeletal formula?
- shows the bonds of the carbon only with any functional groups
- the hydrogen and carbon atoms arent shown
what is the displayed formula?
shows how all atoms are arranged, and all the bonds betweent them
what is a homologous series?
a group of compounds that contain the same functional group.
-they can all be represented by the same general formula
what are the features of a homologous series?
- they have the same functional group
- they react in a similar way
- they have the same general molecular formula
what is nomenclature
the naming of organic compounds
what the rules for nomenclature
- 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-) - 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) - 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.
- 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
for each side group state what the prefix is
CH3
CH2CH2
F
Cl
Br
I
CH3- methyl
CH2CH2- ethyl
F- fluoro
Cl- chloro
Br- bromo
I- iodo
what is the IUPAC system?
what is the benfit of this system?
- 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.
draw the structural, displayed and skeletal formula of cyclohexane
-structural: CH2CH2CH2CH2CH2CH2
what is the IPUAC name for this chemical?
2-methylpentane
answer these summary questions on nomenclature
answers
draw the structure of 2-methylpentane
what is a mechanism?
- 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
what does a curly arrow show?
electron movement
-goes from lone pair of electron to where a new bond is formed at the end of the reaction
what is the free radical susbstituion reaction when halogens react with organic compounds
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
how is a free radical formed?
it is formed when a covalent bond breaks by homolytic fission (equal spitting of a bond) to form a particle with an unpaire electron
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
- 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•
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
- 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)
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
- 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•
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
- 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
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)
(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
what is the disadvantage of free radical substitution?
-a mixture of products and the desired product would have to be seperated from the other products
what is meant by structural isomerism?
this is when chemicals have the same molecular formula but different structural formulae
what are the 3 types of structural isomers?
- chain
- positional
- functional group
what is the difference between chain isomers?
they have different chain lenghts (the carbon chain may go from 4 -bute to 3 -prop)
what is the difference between positional isomers?
- the functional group or side group in poisitional isomers change position
e. g
what is the difference in functional group isomers?
-the difference between functional group isomers is that they have different functional group. Which means they have different homologous series
what are the two types of different stereoisomerism isomers (geometric isomers)
E-Z isomers
what is stereoisomerism (geometric isomers)?
this is where two (or more) compounds have the same structural formula but they differ in the arrangment of the bonds in space
what type of compounds do you find E-Z isomers in?
alkenes
describe what a z isomer looks like
draw the z-isomer of but-2-ene (what is the name of this molecule?)
the z-isomer has the same groups either both above or both below the double bond
this molecule is Z-but-2-ene
describe what an e isomer looks like
draw the e-isomer of but-2-ene (what is the name of this molecule?)
the e-isomer has the same groups positioned across the double bond
this molecule is called E-but-2-ene
way of remembering e-z isomers
- 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’
draw the e-isomer of hex-3-ene
*make sure that you put the CH3 at the end of your chain so that the carbons are only making 4 chains
draw the z-isomer of hex-3-ene
*make sure that you put the CH3 at the end of your chain so that the carbons are only making 4 chains
what is the Cahn-Ingold-Prelog Rules (CIP)?
- 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
