Transcript 07. organic_05mar12

Organic Molecules
• Organic ≡ Carbon based
– Most numerous class of materials
– Countless combinations are possible
– Carbon bonds with almost any other element
• Carbon to carbon bonds very common
– Gases (acetylene, propane)
– Linear chain liquids (gasoline, oil)
– Ring structures (benzene, cyclopentane)
– Crystalline structures (diamond, graphite)
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Hydrocarbons
• Alkane series, linear progression of carbon
– Methane = 1 carbon (natural gas)
– Ethane = 2 carbon (ripening fruit)
– Propane = 3 carbon chain (gas BBQ)
– Butane = 4 carbon chain (cigarette lighters)
– Pentane = 5 carbon chain
– Hexane = 6 carbon chain (Naptha)
– Heptane = 7 carbon chain
– Octane = 8 carbon chain (gasoline reference)
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Fig. 13-12, p. 382
Naptha & Kerosene
Naptha is less dense than gasoline
Kerosene is heavier (same as Jet Fuel)
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Diesel = Heating Oil  Legal Issue
• Chemically very similar
– Home heating oil can be
used in diesel cars, and
vice versa
• Fuel taxed by application
– Road Tax for highway use,
not home heating
– Northeastern states put
dye color in heating oil
– Don’t get caught with
colored fuel in your car!
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Diesel making a comeback
• Longer molecule than
gasoline, more carbon
bonds, greater mileage
• Diesel engines simpler,
more robust & reliable
• Older fuels had more
sulfur, SO2 into the air
• Older design engines also
made lots of soot.
• Fuels now cleaner, and
cars are more efficient.
• Europe about 50/50
gasoline vs diesel cars
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Fractional Distillation of Crude Oil
multitude of carbon lengths & shapes from natural processes
Diesel fuel contains >150 different molecules
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Hydrocarbons
• Linear Hydrocarbons
– “backbone” not branched, continuous (zig-zag) line
• Branched Hydrocarbons
– Molecule has branches, usual term is “iso”
• Iso-octane, Isopropyl
• Ring structures
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–
–
–
Carbon backbone closed in on itself
“aliphatic” no double bonds (e.g. cyclohexane)
“aromatic” with double bonds (e.g. benzene)
“Buckyballs” are closed hollow surfaces (e.g. C60)
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Octane and Iso-Octane
Zig-Zag shape dictated by tetrahedral bonding
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Oxygen based attachments
• Oxygen between carbons is an “ether”
– Ethyl ether is H3C-O-CH3
• Oxygen to side of carbon is a “ketone”
– Acetone is H3C-CO-CH3
• Hydroxyl on carbon is “alcohol”
– Ethanol is C2H5OH
• Carbon with 2 oxygen is “Carboxyl”
– Carboxylic Acid (e.g. vinegar = Acetic Acid)
• Alcohol + Carboxylic acid = “ester”
– Basis of many flavors and odors
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Ethers
Ethers identified by central “–O-”group
• Diethyl Ether (or Ethyl Ether)
– an early general anesthetic, first used 1842
– Low boiling point, extremely flammable
– Used as automotive “starting fluid”
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p. 368
Ketones
Ketones contain branched double bond oxygen on carbon
• Acetone is simplest ketone
– A strong solvent, nail polish remover
– Mixes with water or oil
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Alcohols
Alcohols identified by “-OH” group
• Ethanol, component of alcoholic beverages
– Now considered an “alternative” to Gasoline
– E-85 is 85% ethanol, 15% gasoline
– Some stations in San Jose now offer it
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p. 368
Esters
Combining an alcohol and carboxylic acid
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Esters, common flavors
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E15 motor fuel
• E15 contains 15% ethanol and 85%
gasoline. This is generally the greatest
ratio of ethanol to gas that is
recommended by auto manufacturers that
sell vehicles in the United States, though it
is possible that many vehicles can handle
higher mixtures without trouble. Flexiblefuel vehicles are designed to take higher
concentrations, up to 96% v/v ethanol (and
no gasoline).
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E20 motor fuel
• E20 contains 20% ethanol and 80% gasoline.
This fuel is not yet widely used in the United
States, but will be mandated by the U.S. state of
Minnesota by 2013. Since February 2006, this is
the standard ethanol-gasoline mixture sold in
Brazil, where concerns with the alcohol supply
resulted in a drop in the ethanol percentage,
previously at 25%. Flexible-fuel cars are set up
to run with gasoline in such concentration range
and few will work properly with lower
concentrations of ethanol
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E85 motor fuel
• E85 is a mixture of 85% ethanol and 15% gasoline, and
is generally the highest ethanol fuel mixture found in the
United States. It is common in Sweden, and there are
more than 1000 public E85 fuel pumps in the U.S. as of
2006, mostly concentrated in the Midwest, with over
half of those in Minnesota.
• This mixture has an octane rating of about 105. This is
down significantly from pure ethanol but still much
higher than normal gasoline. The addition of a small
amount of gasoline helps a conventional engine start
when using this fuel under cold conditions.
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Local availability of E-85
• “Flex-Fuel” cars
– Operate with multiple fuels
– Alcohol or Gasoline in Brazil
• Both available at same station
– Motorists buy cheapest one
• Alcohol has 70% mileage of gas
• Alcohol 70% price = breakeven
• Bring your calculator !
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Logo used in the United States
for E85 fuel
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Swedish bus running on E96
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Carbon Cycle
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Swedish Alcohol Fuel Experiment
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Carboxylates
Identified by “-COOH” group (acid form)
• Formic Acid, H-COOH, bee-sting venom
– Acetic acid (vinegar) is H3C-COOH
– Propionic Acid (preservative) H3C-CH2-COOH
– Butyric Acid (rancid butter) H3C-CH2-CH2-COOH
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Fig. 13-19, p. 385
Carboxylic Acid ionization
Hydrogen ion + Carboxylate ion
• Acetic acid ionizes to hydrogen + acetate ion
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P/review, p. 385
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Fig. 13-12, p. 382
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Fig. 13-13, p. 382
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Fig. 13-14, p. 383
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Fig. 13-15, p. 383
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Fig. 13-16, p. 384
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Fig. 13-17, p. 384
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p. 386
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p. 384
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Fig. 13-18, p. 385
Computer Modeling
• CABRILLO COLLEGE has an interactive molecule display,
allowing users to twist and turn common molecules to
investigate their structures. Almost like a video game, but
more educational than killing aliens. We sometimes use
this in lab classes, lots of options to play around with.
• http://c4.cabrillo.edu/chem30a/exercises/Exer_1/index.html
• http://c4.cabrillo.edu/chem30b/exercises/chpt_11_060700/index.html
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