unit 3 organic chemistry chemistry 2202 introduction organic chemistry is the study of the molecular...
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Unit 3Organic Chemistry
Chemistry 2202
Introduction
Organic Chemistry is the study of the molecular compounds of carbon.eg. CH4 CH3OH CH3NH2
Organic compounds exclude oxides of carbon and ions containing carbon.ie. CO CO2 KCN CaCO3
are NOT organic compounds!!
History of Organic Chemistry
Started when medicine men extracted chemicals from plants and animals as treatments and cures
First defined as a branch of modern science in the early 1800's by Jon Jacob Berzelius
Berzelius believed in Vitalism - organic compounds could only originate from living organisms through the action of some vital force
organic compounds originate in living or once-living matter
inorganic compounds come from "mineral" or non-living matter
In 1828, Friedrich Wöhler discovered that urea - an organic compound - could be made by heating ammonium cyanate (an inorganic compound).
NH4OCN(aq) (NH2)2CO(s)
inorganic organic
What’s this?
(NH2) 2CO - (NH2)2CO
di-urea
organic chemistry branched into disciplines such as polymer chemistry, pharmacology, bioengineering and petro-chemistry
98% of all known compounds are organic
The huge number of organic compounds is due mainly to the ability of carbon atoms to form stable chains, branched chains, rings, branched rings, multiple rings, and multiple bonds (double and triple bonds) to itself and to many other non-metal atoms.
Some more Organic notes
Sources of Organic Compounds
1. Carbonized Organic Matter- fossil fuels such as coal, oil, and
natural gas - basis for the petrochemical industry
2. Living Organisms eg: - penicillin from mold
- ASA from the bark of a willow tree
3. Invention
- antibiotics, aspirin, vanilla flavoring, and heart drugs are manufactured from organic starting materials
- plastics
Structural Isomers
Structures that have the same molecular formula but different structural formulas are called structural isomers
eg. C4H10
Practice: Draw all structural isomers of C5H12 and C6H14
Structural Isomers
structural isomers have the same chemical formula but have different chemical and physical properties.
Classifying Organic Compounds Organic
Compounds
Hydrocarbons HydrocarbonDerivatives
• Alcohols• Ethers• Aldehydes• Ketones• Carboxylic Acids• Alkyl Halides• Esters• Amines• Amides
Aliphatic
AlkAnes
AlkEnes
AlkYnes
Aromatic (benzene based)
hydrocarbons consist of carbon
and hydrogen atoms only
eg. Methane - CH4 hydrocarbon derivatives have one
or more hydrogen atoms replaced by another nonmetallic atom
eg. bromomethane - CH3Br
methanol - CH3OH
aliphatic hydrocarbons have carbon atoms bonded in chains or rings with only single, double, or triple bonds
aromatic hydrocarbons contain at least one 6 carbon benzene ring
Aliphatic Hydrocarbons
1. AlkanesAlkanes are hydrocarbons that have
only single bonds between carbon atoms
general formula CnH2n+2
eg. C3H8 C6H14
IUPAC prefixes
Prefix # of carbon atoms
meth 1
eth 2
prop 3
but 4
pent 5
hex 6
hept 7
oct 8
non 9
dec 10
Complete this table for the first 10 alkanes
methane CH4
ethane
propane
A series of compounds which differ by the same structural unit is called a homologous series
eg. each alkane increases by CH2
What is the next member of this homologous series?
SiO2 Si2O3 Si3O4 _____
Representing Alkanes (4 ways)
1. Structural formulas
eg. propane
H – C – C – C – H
HHH
HHH
Hydrogen atoms may be omitted from structural formulas
eg. propane
– C – C – C –
2. Condensed Structural Formula
eg. propaneCH3-CH2-CH3
3. Line Structural Diagrams
eg: propane
(the endpoint of each segment is a carbon atom)
4. Expanded Molecular Formulas
eg. propane
CH3CH2CH3
p. 333
An alkyl group has one less hydrogen than an alkane.
General Formula: CnH2n + 1
To name an alkyl group, use the prefix to indicate the # of carbon atoms followed by the suffix –yl
eg. -C7H15 heptyl
Alkyl Groups
Alkyl Groups
methyl -CH3
ethyl -C2H5 or -CH2CH3
propyl -C3H7 or -CH2CH2CH3
Branched alkanes are alkanes that contain one or more alkyl groups
eg.
Alkyl Groups
1. Find the longest continuous chain of carbons(parent chain) and name it using the alkane name.
2. Number the carbons in the parent chain starting from the end closest to branching. These numbers will indicate the location of alkyl groups.
Naming Branched Alkanes
Naming Branched Alkanes
3. List the alkyl groups in alphabetical order. Use Latin prefixes if an alkyl group occurs more than once. (di = 2, tri = 3, tetra = 4, etc.)
4. Use a number to show the location of each alkyl group on the parent.
5. Use commas to separate numbers, and hyphens to separate numbers and letters.
Naming Branched Alkanes
eg.
7 6 5 4 3 2 1
ethyl
methyl
4-ethyl-3-methylheptane
Naming Branched Alkanes
Practice:p. 336 - 339 #’s 5 – 11
(Answers on p. 375)
Naming Branched Alkanes
Alkenes and Alkynes
saturated hydrocarbons contain only single bonds between carbon atoms
eg. alkanessaturated hydrocarbons have the
maximum number of hydrogen atoms bonded to carbon atoms
Alkenes and Alkynes
unsaturated hydrocarbons contain double or triple bonds between carbon atoms
eg. alkenes and alkynes
Alkenes and Alkynes
General Formulas:
Alkenes CnH2n
Alkynes CnH2n - 2
At least one double bond
At least one triple bond
Naming Alkenes and Alkynes
1. Name the longest continuous chain that contains the double/triple bond.
2. Use the smallest possible number to indicate the position of the double or triple bond.
Naming Alkenes and Alkynes
3. Branches are named using the same rules for alkanes.
4. Number the branches starting at the same end used to number the multiple bond.
Naming Alkenes and Alkynes
p. 347 #’s 17 - 19p. 354 #’s 28 & 29
Cyclic Hydrocarbons
Pp. 356 – 358questions 30 & 31
cyclopentane
methylethyl
1-ethyl-3-methylcyclopentane
3-ethyl-1-methylcyclopentane
1
2
3
methyl
1,2,3,4-tetramethylcyclohexane
Aromatic Compounds
Aromatic hydrocarbons contain at least one benzene ring.
The formula for benzene, C6H6 , was determined by Michael Faraday in 1825.
The structural formula was determined by August Kekulé in 1865.
Aromatic Compounds
Proposed formula:
Conflicting Evidence
C=C double bonds are shorter than C-C single bonds. X-ray crystallography shows that all C-C bonds in benzene are the same length.
Benzene reacts like an alkane, not like an alkene.
Modified structure
Kekulé proposed a resonance structure for benzene.
The resonance structure is an average of the electron distributions.
Aromatic Compounds
or
Aromatic Compounds
bonding electrons, once believed to be in double bonds, are delocalized and shared equally over the 6 carbon atoms
the bonds in benzene are like “1½” bonds – somewhere between single and double.
Naming Aromatic Compoundsan alkyl benzene has one or more H
atoms replaced by an alkyl group.name the alkyl groups, using
numbers where necessary, followed by the word benzene.
Aromatic Compounds
methylbenzene
propylbenzene
ethylbenzene
Aromatic Compounds
1,3-dimethylbenzene
1,4-dimethylbenzene
1,2-dimethylbenzene
Aromatic Compounds
ortho- means positions 1 and 2 and is represented by "o"
meta- means positions 1 and 3 and is represented by "m"
para- means positions 1 and 4 and is represented by "p"
Aromatic Compounds
m-dimethylbenzene
p-dimethylbenzene
o-dimethylbenzene
Aromatic Compounds
Benzene is treated as a branch if it is not attached to the terminal carbon of an alkyl group
Benzene as a branch is called phenyl
Aromatic Compounds
CH2
CH2
CH3
CH3CHCH3
propylbenzene2-phenylpropane
Aromatic Compounds
CH3CHCHCH2CH2CH3
CH2CH3
Aromatic Compounds
CH3CHCHCH2CHCH2CH2CH3
CH2
CH2
CH3
CH3
Aromatic Compounds
p. 361 #’s 32 – 35
Hydrocarbons Practice
pp. 363, 364
#’s 4 – 9
Test!!
cis and trans isomers (p. 348)
Properties of aliphatic hydrocarbons
Because they are nonpolar, all hydrocarbons are insoluble in water.
The boiling point of alkanes is somewhat higher than alkenes but lower than alkynes.
As the number of atoms in the hydrocarbon molecule increases, the boiling point increases.
Reactions
Complete the aliphatic hydrocarbons worksheet using these references:
a) complete combustion (p. 340)
b) incomplete combustion (p. 340)
c) substitution reaction (p. 344, 362)
d) addition reaction (p. 349)
Hydrocarbon Derivatives
hydrocarbon derivative - contains other nonmetal atoms such as O, N, or halogen atoms.
9 types functional group - the reactive group
of atoms that gives a family of derivatives its distinct properties
Hydrocarbon Derivatives
The general formula for a derivative is
R - functional group
where R stands for any alkyl group.
Hydrocarbon Derivatives
eg. ALCOHOLS R-OH
ethanol C2H5OH
propanol C3H7OH
CARBOXYLIC ACIDS R-COOH
ethanoic acid CH3COOH
propanoic acid C2H5COOH
1. Alcohols
Have the hydroxyl functional group
General Formula: R - OH
Naming Alcohols (p. 387)
The parent alkane is the longest chain that has an -OH group
Replace the last -e in the alkane name
with the suffix -ol.Add a number to indicate the location of
the -OH group.
C OH
H
H
H
CC O
H
H
H
H
H
H
methanol
ethanol
eg. CCC O
H
H
H
H
H
H
H
H
CCC
O
H
H
HH
H
H
H
H
Properties of Alcohols (p. 389)
Alcohols have H-bonding which makes their mp and bp higher than the corresponding alkane.
Polarity decreases as the # of carbon atoms increases
Long chain alcohols are less soluble in water than short chain alcohols.
Reactions of alcohols
Combustion
R-OH + O2 → CO2 + H2O
eg. Write the equation for the burning of butanol.
Reactions of alcohols
Substitution
R-OH + H-X → R-X + H2O
eg. Use structural formulas to show the reaction between 2-pentanol and HBr.
Reactions of alcohols
Elimination (Dehydration)
eg.
CCC OH
H
H
HHH
HH
H2SO4CCC HHH
HH
H
+ H2O
P. 393 16 a), d), 18 a), b), d) & e)
(Draw structural formulas for the products in #18)
2. Ethers
Composed of two alkyl groups bonded to an oxygen atom.
General Formula: R1-O-R2
Naming ethers: p. 395IUPAC nameCommon name
O C C
H
H
H
H
H
CH
H
H
O C C C C
H
H
H
H
H
H
H
H
H
CCC
H
H
H
H
H
H
H
O C C
H
H
H
H
H
CC
H
H
H
H
H
P. 395, 396 #’s 20 – 23
Worksheet: Ethers
3. Aldehydes (p. 402)
Contain a carbonyl functional group at the end of a carbon chain.
General Formula:- =
HR-C
O
Naming:Use the alkane name for the longest
continuous chain.Remove the –e and add the suffix –aleg.
butane → butanal
CCCC O
HH
H
H
H
H
H
H
4. Ketones (p. 402)
Contain a carbonyl functional group in the ‘middle’ of a carbon chain.
ie. NOT on carbon #1
General Formula:
=O
- R2R1-C
Naming:Use the alkane name for the longest
continuous chain.Replace the –e with the suffix –oneUse the smallest possible number for
the position of the C=O group.
CCCC
O
H
H
H
H
H
H
H
H
CCCCC
O
H
H
H
H
H
H
H
H
H
H
p. 403 #’s 28 - 31
Handout: Aldehydes and Ketones
5. Carboxylic Acids (p. 405)
Contain a carboxyl functional group
ie. -COOH
General Formula:
AKA: Organic Acids
=O
- OHR1-C
CCC OH
OH
H
H
H
H
Text; p. 406 #’s 32 - 35
C C C CO
O H
H
H
H
H
H
H
H
6. Alkyl Halides (p. 390, 391)
Contain at least one halogen atom
General Formula: R – X
(X is F, Cl, Br, or I)
Text; p. 391 #’s 12 – 15
Worksheet: Organic # 8
CCCC
Br
Br
Br
H
H
HH
H
H
H
CCCCC
Cl
Br
BrBr
Br
H
HHH
H
H
H
Text; p. 406 #’s 32 - 35
Elimination - Alcohols
eg.
CCC OH
H
H
HHH
HH
H2SO4CCC HHH
HH
H
+ H2O
Δ
Elimination – Alkyl Halides
eg.
CCC I
H
H
H
H
H
H
H
+ H2O + I-
+ OH- → CCC H
HH
H
H
H
p.393 #’s 18 c) and f)
7. Esters (pp. 410, 411)
Form when a carboxylic acid reacts with an alcohol
General Formula:
Esterification Reaction:carboxylic acid + alcohol → ester + water
=
- O-R2R1-C
O
Naming:
- the parent is named by replacing the
– oic acid ending from the acid with – oate
- the alcohol is identified by using the corresponding alkyl group
pp. 411, 412 #’s 36 - 40
8. Amines (pp. 410, 411)
Form when a carboxylic acid reacts with an alcohol
General Formula: R – NH2
Cracking & Reforming
‘Cracking‘ is a reaction that break long chain hydrocarbons into smaller fragments.
eg.
decane + H2 → ethane + octane
Reactions – Organic Compounds
Combustion (p. 340)
Substitution (p. 344)
Esterification (p. 410)
Elimination (p. 390)
Cracking & Reforming
‘Reforming’ is a reaction that combines smaller hydrocarbons to make long chain hydrocarbons
eg.
ethane + butane → hexane + H2
Review - Derivatives
pp. 400, 401
Omit: 1a), 2c) & d), 3b) & e), 5b),
8, 10b) & c), 11b) & d)
pp. 419, 420
Omit: 1g), 3d), 4a), 7, 8c), 10