What is organic chemistry
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Transcript of What is organic chemistry
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What is organic chemistryAn organic compound • is a compound made from carbon atoms.• has one or more C atoms. • has many H atoms.• may also contain O, S, N, and halogens
Typical organic compounds• have covalent bonds.• have low melting points.• have low boiling points.• are flammable.• are soluble in nonpolar solvents.• are not soluble in water.
oil (organic) and water (inorganic)
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Organic vs. Inorganic
• Propane, C3H8, is an organic compound used as a fuel.
• NaCl, salt, is an inorganic compound composed of Na+ and Cl- ions.
Recall carbon’s properties!
In organic compounds • carbon has 4 valence electrons and hydrogen
has 1.
• •C • H •
•
• to achieve an octet, C forms four bonds. H H
H C H H C H
H H CH4 ,
methane
carbon atom with four single, covalent bonds, has a tetrahedral shape
Organic molecules have….
In organic molecules, • valence electrons are shared.• covalent bonds form between carbon atoms.
H H H H • • • •
H C C H H C C H
• • • • H H H H
ethane, CH3─CH3
What are alkanes?
Alkanes are written with structural formulas that are
• expanded to show each bond.• condensed to show each carbon atom and its
attached hydrogen atoms.
Expanded Condensed H
H C H CH4 , methane
H
Expanded vs condensed!
Condensed formulas are written for expanded structural formula by showing each carbon and the attached hydrogen atoms.
Expanded Condensed H H H H │ │ │ │H─C ─C ─C ─C ─ H CH3─CH2─CH2─CH3
│ │ │ │ H H H H
How to name alkanes?The names of alkanes • are determined by the IUPAC (International Union of Pure and Applied
Chemistry) system.• end in –ane.• with 1-4 carbons in a chain use prefixes as follows.Name # Carbons Structural Formula
Methane 1 CH4
Ethane 2 CH3CH3
Propane 3 CH3CH2CH3
Butane 4 CH3CH2CH2CH3
Pentane 5 CH3CH2CH2CH2CH3
Hexane 6 CH3CH2CH2CH2CH2CH3
Heptane 7 CH3CH2CH2CH2CH2CH2CH3
Octane 8 CH3CH2CH2CH2CH2CH2CH2CH3
Nonane 9 CH3 CH2
CH2CH2CH2CH2CH2CH2CH3
Decane 10
CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3
Learning Check
A. Write the condensed formula for: H H H H H
H C C C C C H H H H H HB. What is its molecular formula?C. What is its name?
A. CH3─CH2─CH2─CH2─CH3
B. C5H12
C. pentane
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Writing Structural Formulas
Carbon atoms in a chain• maintain tetrahedral shape.• are connected in a zig-zag pattern.• are drawn as 2-dimensional. • Ccan be written in several conformations.
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Hexane has Six Carbon Atoms
Hexane • is an alkane with six carbon atoms in a
continuous chain.• has a “zig-zag” look because each carbon
atom is at the center of a tetrahedron.• is represented by a ball-and-stick model as
shown below.
What are cycloalkanes?
Cycloalkanes
• are cyclic alkanes.• have two hydrogen atoms fewer than the
open chain.• are named by using the prefix cyclo- before
the name of the alkane chain with the same number of carbon atoms.
Learning check
Name the following.
A. CH3─CH2─CH2─CH3
B.
C. CH3─CH2─CH2─CH2─CH2─CH2─CH2─CH3
D.
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Need to use substituent with alkanes
Isomers of Butane• have the same molecular formula.• have different atom arrangements.• of butane (C4H10) are a straight chain and a
branched chain. Alkyl groups are• alkanes that are missing one H. • substituents attached to carbon chains.• named with a –yl ending.• CH3 methyl
• CH3 CH2 ethyl
Alkanes with substituents
CH3
CH3 CH CH3
methylpropane
methyl groups
CH3 CH3
CH3 CH CH2 CH CH3 2,4-
dimethylpentane
Naming alkanes
Give the name of CH3 CH3
CH3─CH─CH─CH3
STEP 1 Name the longest continuous chain.
CH3 CH3
CH3─CH─CH─CH3
butane
Naming Alkanes
Give the name of CH3 CH3
CH3─CH─CH─CH3
STEP 2 Number chain. CH3 CH3
CH3─CH─CH─CH3
1 2 3 4STEP 3 Locate substituents and name.
2,3-dimethylbutane
Let’s practice again!
STEP 1 Longest chain is pentane.
STEP 2 Number chain from end nearest substituent.
Cl CH3
CH3─CH2─CH─CH─CH3
5 4 3 2 1
STEP 3 Locate substituents and name alphabetically.
3-chloro-2-methylpentane
Learning Check
Give the IUPAC name for each of the following:
A. CH3 CH3
| | CH3─CH─CH2 ─CH─CH3
B. Cl CH3 | |
CH3─CH2─CH─CH2─C─CH2─CH3
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Cl
Learning Check
Draw the condensed structural formula for 2-bromo-1-chlorobutane.
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Naming Cycloalkanes with Substituents
The name of a substituent is placed in front of the
cycloalkane name.
methylcyclobutane CH3
chlorocyclopentane Cl
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Learning Check
Name each of the following.
1. CH3
CH2─ CH3
2.
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Some Properties of AlkanesAlkanes are• nonpolar.• insoluble in water.• less dense than water.• flammable in air. Alkanes with 1-4 carbon atoms are• methane, ethane, propane, and butane.• gases at room temperature.• used as heating fuels.Alkanes with 5-8 carbon atoms are• liquids at room temperature.• pentane, hexane, heptane, and octane.• very volatile.• used to make gasoline.Alkanes with 9-17 carbon atoms • are liquids at room temperature• have higher boiling points.• are found in kerosene, diesel, and jet fuels
Alkanes with 18 or more carbon atoms• have high molar masses.• are waxy solids at room
temperature.• used in waxy coatings of
fruits and vegetables.
Reactions of alkanes: Combustion
In combustion reactions,• alkanes react with oxygen. • CO2, H2O and energy are produced.
Alkane + O2 CO2 + H2O + heat
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Learning CheckWrite a balanced equation for thecomplete combustion of propane
Unbalanced equation
C3H8 + O2 CO2 + H2O
Balance C
C3H8 + O2 3CO2 + H2O
Balance H
C3H8 + O2 3CO2 + 4H2O
Balance O
C3H8 + 5O2 3CO2 + 4H2O
(Balanced)
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Other elements in organic compounds
In organic molecules,
carbon atoms bond • with four bonds.• mostly with H
and other C atoms.
• sometimes to O, N, S,
• sometimes to halogens F, Cl, and Br.
Functional groups are• a characteristic feature
of organic molecules that behave in a predictable way.
• composed of an atom or group of atoms.
• groups that replace a hydrogen atom in the corresponding alkane.
• a way to classify families of organic compounds.
What are functional groups?