Transcript Document

Organic and Biological Molecules
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Organic chemistry is all about
carbon compounds, the element
of living organisms.
To name organic compounds,
you will use prefixes to indicate
the number of atoms present.
Meth = one
Eth = two
Prop = three
But = four
Pent = five
Hex = six
Hept = seven
Oct = eight
Non = nine
Dec = ten
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Boiling points reflect the strength of forces
between molecules. The more they stick
together, the more energy it will take to blast
them into the atmosphere as gases.
The relative strength of the four intermolecular
forces is: Ionic >hydrogen bonding>dipole
dipole>van der Waals (London dispersion)
forces.
Boiling points increase as the number of
carbons increase.
Branching decreases boiling point.
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Among molecules with roughly similar
molecular weights, the boiling points will be
determined by the functional groups present.
Bigger molecules have higher boiling points.
When the number of electrons increase, the
temporary dipole attractions increase which
then increases the dispersion forces. So the
bigger the molecule, the “stickier” they are to
each other.
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Long thin molecules can develop bigger
temporary dipoles due to electron movement
more so than short fat ones containing the same
number of electrons. The top molecule is a 2methylpropane and the bottom is a butane
molecule. Which one would have the higher
boiling point?
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Molecules with permanent dipole –dipole
attractions will have a higher boiling point then
those with temporary fluctuating dipoles.
Compare fluoromethane and ethane. Both
have the same number of electrons and are the
same size, but one has a permanent dipoledipole attraction. Which one has the higher
boiling point?
Ethane
Fluoromethane
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Carbon and hydrogen
compounds with single
bonds:
Methane
Ethane
Propane
Butane
Pentane
Hexane
Heptane
Octane
Nonane
Decane
Formula: CnH2n+2
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These have multiple
bonds somewhere in
the alkane chain.
An example is ethene,
also known as
ethylene: C2H4
These typically
readily undergo rapid
addition reactions.
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The larger molecules can form
different structures.
To name them, you first look for
the longest continuous carbon
chain. In this case its propane.
Then you need to indicate how
many chlorines there are and
where they are located on the
carbon chain.
First one is a 1-chloropropane.
Second one is a 2-chloropropane.
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Octane
2-Methylheptane
3-Methylheptane
4-Methylheptane
2,2-Dimethylhexane
2,3-Dimethylhexane
2,4-Dimethylhexane
2,5-Dimethylhexane
3,3-Dimethylhexane
3,4-Dimethylhexane
3-Ethylhexane
2,2,3-Trimethylpentane
2,2,4-Trimethylpentane
2,3,3-Trimethylpentane
2,3,4-Trimethylpentane
2-Methyl-3-ethylpentane
3-Methyl-3-ethylpentane
Tetramethylbutane
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These rings typically
do not undergo
addition reactions like
other unsaturated
hydrocarbons.
Instead, they tend to
undergo substitution
reactions where
hydrogens are
replaced by other
atoms.
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Polymers are large, usually chainlike molecules
that are built from smaller molecules called
monomers. This is where plastic comes from…
Monomer
Polymer
Uses
Ethylene
Polyethylene
Plastic piping, bottles,
electrical insulation, toys
Propylene
Polypropylene
Film for packaging,
carpets, lab wares, toys
Vinyl chloride
Polyvinyl chloride (PVC)
Piping, siding, floor tile,
clothing, toys
Acrylonitrile
Polyacrylonitrile
Carpets, fabrics
Tetrafluoroethylene
Teflon
Cooking utensils,
electrical insulation,
bearings
Styrene
Polystyrene
Containers, thermal
insulation, toys
Butadiene
Polybutadiene
Tire tread, coating resin
Butadien and styrene Styrene-butadiene rubber
Synthetic rubber
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Proteins are natural
polymers where the
building blocks are
amino acids.
Through
condensation
reactions, the amide
group forms
polypeptide chains
that eventually yield a
protein.
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When writing organic formulas, make sure that
every carbon has four bonds.
When naming alkanes, make sure to number
the carbon chain so the sum of all location
numbers is as small as possible.
When naming branched alkanes, be sure to
consider the branches when finding the longest
carbon chain.
In naming identical substituents on the longest
carbon chain, be sure to use repeating location
numbers, separated by commas (2,2-dimethyl).
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The alkane hexane, C6H14, has a molecular mass of
86.17 g/mol.
Like all hydrocarbons, hexane will burn. Write a
balanced chemical equation for the complete
combustion of hexane. This reaction produces
gaseous carbon dioxide, CO2 and water vapor,
H2O. (you knew that!)
2C6H14 + 19 O2  12 CO2 + 14 H2O
Give yourself 2 points for the answer shown above
or for the coefficients 1, 9/2, 6, and 7.
Give yourself 1 point if you have one or more, not
all, of the elements balanced.
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The combustion of 10.0 g of hexane produces
487 kJ. What is the molar heat of combustion
(ΔH) of hexane?
(-487 kJ/10.0g)(86.17 g hexane/mol) = -4.20 x
103 kJ/mol
Give yourself 2 points for the above setup and
correct answer (this requires a negative sign in
the answer). If the setup is partially correct,
give yourself 1 point.
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Determine the pressure exerted by the carbon
dioxide formed when 5.00 g of hexane is
combusted. Assume the carbon dioxide is dry and
stored in a 20.0 L container at 27oC.
P = nRT/V
(5.00 g C6H14 ) (1 mol C6H14/86.17 g C6H14)(12 mol
CO2/2 mol C6H14) = 0.348 mol CO2
The mole ratio should match the one given in your
balanced equation. You will not be penalized
again for an incorrectly balanced equation.
You will lose a point if you do not include a
hexane to CO2 conversion.
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R = 0.08206 L· atm/mol · K
T = 27oC + 273 = 300.0 K
V = 20.0 L
P = (0.3481 mol CO2)(0.08206 L· atm/mol ·
K)(300.0 k)/20.0 l = 0.429 atm
Give yourself 2 points for the correct setup and
answer. Give yourself 1 point if you did
everything correctly, except the mole ratio or the
Kelvin conversion.
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Hexane, like most alkanes, may exist in different
isomeric forms. The structural formula of one of
these isomers is pictured below. (not really, there
is no Internet to get the picture  so assume it’s a
straight-chain, n-alkane) Draw the structural
formula of any two other isomers of hexane. Make
sure all the carbon atoms and hydrogen atoms are
shown.
Give yourself 1 point for each correct answer, with
a 2-point maximum. There are no bonus points for
additional answers.
Total your points. The maximum 8 points.
Subtract one point if all your answers do not have
the correct number of significant figures.