ORGANIC CHEMISTRY
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Transcript of ORGANIC CHEMISTRY
ORGANIC CHEMISTRY Organic chemistry is the study of carbon containing
compounds derived from living organisms.
Oil is formed over millions of years from the break down of dead creatures and plants.
80+ million compounds-
natural & synthetic.
Crude Oil (petroleum) is a mixture of many thousands of these different compounds and is the main source of many of these chemicals.
They are called hydrocarbons because they predominantly contain the elements hydrogen and carbon.
Distillation of Crude Oil
Distillation of Crude Oil
Homologous series
This is a series of compounds which all contain the same functional group, and have similar chemical properties.
ALKANES ALKENES ALCOHOLS
CH4 CH2 =CH2 CH3OH
CH3-CH3 CH2 =CH –CH3 CH3CH2OH
Each has a general formula:
ALKANES: CnH2n+2
The members of the series differ by the number of CH2 units.
CH3-CH3, CH3-CH2-CH3, CH3-CH2-CH2-CH3
Graduation in physical properties: eg: boiling points.
CH4 (GAS), C8H18 (LIQUID), C30H62 (SOLID)
ALKANES SATURATED HYDROCARBONS – contain maximum
amount of hydrogen - only single bonds (no multiple bonds)
GENERAL FORMULA CnH(2n+2)
NAMING ALKANESNo of C atoms
Prefix
1 Meth
2 Eth
3 Prop
4 But
5 Pent
6 Hex
7 Hept
8 Oct
All alkanes end with ‘ANE’.
All belong to the same HOMOLOGOUS series
Alkenes
Esters
Amines
(alcohol)~yl
(acid)~oate
Amino -
CH3CONH2
Acylchlorides
Amides
~oyl Chloride
~amide
Aldehydes
Carboxylic Acids
~al
~oic acid
CH3- IHaloalkanes
Ketones
Halo~
~one
CH2 = CH2
Alcohols
~ene
~olFunctional
groups
The functional groups are
atoms or
combinations of atoms which determine the
properties of organic molecules.
STRUCTURES OF ALKANES
METHANE CH4
Bond Angle 109.5o Shape Tetrahedral
Can be illustrated as:
H
H C H
H
ETHANE. Molecular formula C2H6
Structural formula: CH3 CH3 or H H
H C C H
H H
PROPANE.
Molecular formula: C3H8Structural formula: CH3 CH2 CH3 or H H H
H C C C H
H H H
Both ethane and propane are “straight” chain moleculesBUT!! Bonds are NOT 90o molecules are NOT STRAIGHT!!!
Schematic formula
Molecular formula: C4H10 - can have two different structures
“Straight” chain. CH3 CH2 CH2 CH3 BUTANE
Branched chain CH3 CH CH3
CH3
METHYL PROPANE
IsomersIsomers
Compounds that have the same molecular formula but different structural formula.
branch
BUTANE & ISOMERS.
Schematic formula:
TASK:
Illustrate the structures of the three different isomers of C5H12.
Names & StructuresExamples2- methylbutane
CH3
CH3 CH CH2 CH3
CH3
CH3 C CH3
CH3
2,2 – dimethyl propane
TASK: illustrate the structures of:
2-methylpentane.
2,3 – dimethylbutane.
2,2,3 -trimethylpentane
CH3CH(CH3)CH2CH2CH3
CH3CH(CH3)CH(CH3)CH3
CH3C(CH3)2CH(CH3)CH2CH3
THE RULES FOR NAMING ORGANIC COMPOUNDS1. Choose the longest unbroken chain of Carbon atoms and assign a name
for the carbon chain using the prefixes; meth-1, eth-2 etc.
2. Identify any carbon chain branches (alkyl groups). These are assigned names using the same prefixes as above along with the suffix “-yl” – methyl, ethyl etc.
3. Identify the functional groups present in the molecule. Assign a prefix or suffix according to their homologous series. These will be written in front of the name of the carbon chain.
4. There is an order of precedence, to decide the suffix for the carbon chain:
COOH / C=C > OH > Br / Cl
5. Number the Carbon atoms in the longest chain so that the branches/functional groups have the lowest number possible. Allocate a number for every group/branch no matter how many times it occurs. Where groups are on the same carbon write their names in alphabetical order.
6. Numbering takes precedence "wins" over alphabetical spelling. Prefixes are used for groups that occur more than once.
Di – 2 Tri – 3 Tetra – 4 Penta – 5 etc.
7. The final name is written as one word with commas between numbers, hyphens separating numbers from words.
Give the names of the following alkanes(a)CH3 CH2 CH CH2 CH3
CH3
(b) CH3 CH CH2 CH CH3
CH3 CH3
(c) CH3 C(CH3)2 CH2 CH(CH3) CH2 CH3
(d) CH3CH2CH(CH3)C(CH3)3
Give the names of the following alkanes
3-methyl pentane
2,4-dimethylpentane
2,2,4-trimethyl
hexane
(a)CH3 CH2 CH CH2 CH3
CH3
(b) CH3 CH CH2 CH CH3
CH3 CH3
(c) CH3 C(CH3)2 CH2 CH(CH3) CH2 CH3
(d) CH3CH2CH(CH3)C(CH3)3 2,2,3-trimethylpentane
Cyclic Alkanes
When C atoms bond together to form a ‘ring’ – known as a ‘cyclic’ structure.
What is the molecular formula of this alkane?
How does the molecular formula compare to the general formula for alkanes?Why does it belong to the series of alkanes?
Example
Illustrate the cyclic structures of (a) C4H8
and (b) C5H10 and name the molecules.
CYCLOHEXANE
Can you think of a name for this molecule
The shape around the double bond is planar.
The bond angle around the double bond is 120o
C C bond
PLANAR 120o
Represented as C C
Structure of Alkenes
Examples of Alkenes
………………, C2H4
H H
C C
H H
OR …………………….
PROPENE CH2 CH CH3
TASK: Use ball & stick models or sketches to construct and name 3 different structures for C4H8 each one with one double bond.
Examples of Alkenes
ETHENE, C2H4
H H
C C
H H
OR CH2 CH2
PROPENE CH2 CH CH3
TASK: Use ball & stick models or sketches to construct and name 3 different structures for C4H8 each one with one double bond.
CH3CH2CH CH2
CH3CH CHCH3
CH3C CH2
CH3
BUT-1-ENE
BUT-2-ENE
METHYL PROPENE
H H
C C
H CH3
More AlkenesIllustrate structures of the following alkenes:Pent-1-eneHex-3-ene
2-methylbut-1-ene
Cyclohexene
Name the following alkenesCH3CH CHCH2CH3
CH2 CHCH(CH3)CH2CH3CH3CH(CH3)CH CHCH2CH3(CH3)3CCH C(CH3)2
More AlkenesIllustrate structures of the following alkenes:Pent-1-eneHex-3-ene
2-methylbut-1-ene
Cyclohexene
CH2 CHCH2CH2CH3
CH3CH2CH CHCH2CH3
CH2 C(CH3)CH2CH3
Name the following alkenesCH3CH CHCH2CH3
CH2 CHCH(CH3)CH2CH3
Pent-2-ene3-methylpent-1-
eneCH3CH(CH3)CH CHCH2CH3
2-methylhex-3-ene
(CH3)3CCH C(CH3)2 2,4,4-trimethylpent-2-ene
GEOMETRIC ISOMERS There is no rotation about the double bond.
Geometric isomerism is a form of STEREOISOMERISM –
Same molecular and structural formula but atoms are arranged differently in space
GEOMETRIC ISOMERISM each C atom in the double bond has two different atoms/groups attached.
BUT–2-ENE CH3 CH CH CH3
CH3 CH3
C C
H H
CH3 H
C C
H CH3
cis but-2-enetrans but-2-ene
Alkynes
H-C≡C-H
H-C≡C-CH3
H-C≡C-CH2-CH3
CH3-C≡C-CH3
Ethyne
propyne
But–1-yne
But–2-yne
Very reactiveTriple bond unstable!Attracts electrophiles.
General formula CnH(2n+1)X
Substituted alkaneSubstituted alkane with at least one with at least one halogen halogen atomatom
Structures & Names
CH3Cl chloromethaneCH3–CH2 –CH2Br 1- bromopropane
2- iodobutane CH3–CH–CH2 CH3
I
CH3–CH2–CH2–CH2Br PRIMARY 10
CH3–CH2–CH–CH3
Br
SECONDARY 202-bromobutane
TERTIARY 30
2-bromo-2-methylbutaneCH3 CH2–C–CH3
CH3
BrBr
1- bromobutane
General formula CnH(2n+1)OH
•CH3OH Methanol •CH3CH2OH Ethanol
•C3H7OH – two isomers
CH3—CH2—CH2OH
Propan-1-ol 1o
Propan-2-ol 2o
CH3—CH—CH3
OH
TASK: C4H9OH has 4 isomers. Draw the structures of each isomer giving the name and class of each one.
Hydroxyl group
•FERMENTATION – sugars (glucose)/yeast/25oC – 35OC C6H12O6
yeast 2C2H5OH + 2CO2
•HYDRATION OF ETHENECH2=CH2 + H2O CH3CH2OH
Advantage Disadvantage
Fermentation
Hydration
Renewable sourcesLow
energyCheap
Batch
Slow
Impure/Low yieldFast
Pure
High yield /continuous
High energyNon-
renewableExpensive
KNOWN AS CARBONYLS
STRUCTURE C O
BOND ANGLE 120O
ALDEHYDES
GENERAL STRUCTURE
R
C O
H
EXAMPLES
HCHO - methanalCH3CHO - ethanal
CH3CH2CHO - NAME?
Illustrate the structures of these examples
KETONES
GENERAL FORMULAR
C O
R1
R and R1 may be the same or different
EXAMPLES
CH3COCH3 propanoneCH3COCH2CH3 butanoneCH3CH2COCH2CH3 pentan-3-one
Illustrate the structures of these examples – show & name the corresponding aldehyde isomer.
NOTE: ALDEHYDES & KETONES EXHIBIT FUNCTIONAL GROUP ISOMERISM
Carboxylic Acids
GENERAL FORMULA
EXAMPLESHCOOH ................... acidCH3COOH .................... acidCH3CH2COOH .......................... acid
Illustrate the structures of these examples – show & name the corresponding aldehyde isomer.
Acidic reaction
CH3COOH + H2O ……………………………. + H3O+
R
C O
OH
Carboxyl group
-COOH
Carboxylic Acids
GENERAL FORMULA
EXAMPLESHCOOH methanoic acidCH3COOH ethanoic acidCH3CH2COOH propanoic acid
Illustrate the structures of these examples – show & name the corresponding aldehyde isomer.
Acidic reaction
CH3COOH + H2O CH3COO- + H3O+
R
C O
OH
Carboxyl group
-COOH
FORMATION OF ESTERS• GENERALLY: .........+ ........... ESTER + WATER catalysed by H+ ions normally from conc. H2SO4
O O R C + H O R/ R C + H2O
OH O R/
O OH C + CH3OH H C + H2O
OH O CH3
methanoic methanol ............. ..........................
CH3CH2OH + CH3CH2COOH CH3CH2........CH2CH3 + H2O
ethanol propanoic ............ .........................
FORMATION OF ESTERS• GENERALLY: ACID + ALCOHOL ESTER + WATER catalysed by H+ ions normally from conc. H2SO4
O O R C + H O R/ R C + H2O
OH O R/
O OH C + CH3OH H C + H2O
OH O CH3
methanoic methanol methyl methanoate
CH3CH2OH + CH3CH2COOH CH3CH2COOCH2CH3 + H2O
ethanol propanoic ethyl propanoate
NAMING OF ESTERSGENERALLY:
ACID + ALCOHOL ESTER + WATER
ESTER NAME: .......................YL ............ANOATE
CH3CH2OH + CH3CH2COOH CH3CH2COOCH2CH3 +H2O
ethanol propanoic .........yl ............anoate
methanoic methanol..............hyl ..........anoate
NAMING OF ESTERSGENERALLY:
ACID + ALCOHOL ESTER + WATER
ESTER NAME: ALCOHOLYL ACIDANOATE
CH3CH2OH + CH3CH2COOH CH3CH2COOCH2CH3 +H2O
ethanol propanoic ETHyl PROPanoate
methanoic methanol METHyl METHanoate
HYDROLYSIS OF ESTERS• Hydrolysis can take place in either acid or alkaline
solution• Hot alkaline solution is usually preferred• Ester is hydrolysed to alcohol and sodium salt of
acid. Generally RCOOR’ + NaOH ROO-Na+ + R’OH
EXAMPLESCH3COOCH2CH3 + NaOH CH3COO-Na+ + CH3CH2OH
ethyl ethanoate sodium ethanoate ethanolCH3CH2COOCH3 + NaOH CH3CH2COO-Na+ + CH3OH
methyl propanoate sodium propanoate methanol
• Addition of dil.H2SO4 or dil. HCl to sodium salt regenerates the carboxylic acid.
USES OF ESTERS
esters have characteristic sweet smells and are used as food .................
they are also widely used as ............
and as ...................
USES OF ESTERS
esters have characteristic sweet smells and are used as food flavourings.
they are also widely used as solvents
and as plasticisers
NATURALLY OCCURING ESTERS
• Occur as fats and oils, known as triglycerides• Triesters of long-chain carboxylic acid and
propane –1,2,3-triol (glycerol).• On hydrolysis using hot NaOH, 3 moles of long
chain acid are produced together with 1 mole of glycerol.
C17H35COOCH2 CH2OH
C17H35COOCH + 3NaOH CHOH + 3C17H35COONa
C17H35COOCH2 CH2OH sodium
glycerol stearateSodium stearate is used in the manufacture of
soap.
AMINES
NC
H
HH
H
H
N H
H
H
N
H
H
H
NC
HH
H
H
H
AMIDESO
NCC
H
HH
H
H
C
O
NCC
H
H
H
H
H
HH C
O
NCC
H
C
H
H
H
HH
H
HH
Physical PropertiesRecognize and apply to particular examples the relationship between melting
points, boiling points, vapour pressure, viscosity and intermolecular forces (hydrogen bonding, Van der Waals forces including dispersion or London forces number and type of functional group, chain length, branched chains)
Addition reactions• Unsaturated compounds undergo addition reactions to form saturated
compounds e.g.
CH2=CH2 + Cℓ2 → CH2Cℓ-CH2Cℓ -
• hydrohalogentaion - addition of HX - halogenation - addition of X2 –
• hydration - addition of H2O –
• The X-atom or OH-group attaches to the more substituted C-atom.)
• hydrogenation - addition of H2 (During additon of HX and H2O to unsaturated hydrocarbons, the H-atom attaches to the C-atom already having the greater number of H-atoms. ·
Elimination reactions• * Saturated compounds (haloalkanes, alcohols, alkanes) undergo
elimination reactions to form unsaturated compounds e.g. CH2Cℓ-CH2Cℓ → CH2=CHCℓ + HCℓ
• - dehydrohalogentaion - elimination of HX from a haloalkane (alkene with the more highly substituted double bond is the major product). –
• dehydration - elimination of H2O from an alcohol (alkene with the more highly substituted double bond is the major product). –
• dehydrogenation - elimination of H2 from an alkane. - cracking of alkanes. ·
Substitution reactions• * Reactions of HX with alcohols e.g. (CH3)3OH + HBr → (CH3)3Br
+ H2O
• Reactions where the OH of alcohols are substituted with a halogen e.g. (CH3)3Br + KOH → (CH3)3OH + KBr
• Two types of saturated structure can be inter-converted by substitution as shown in the above two reaction equations.
• * Reactions of X2 with alkanes in the presence of light (prior knowledge from Grade 11).