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24 Cards in this Set
- Front
- Back
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paraffins
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a word sometimes used for alkanes
Latin for "little affinity" |
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What does hν mean?
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ultraviolate light
(where ν is the Greek letter nu) |
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Alkanes show regular ______ in both boiling point and melting point as molecular ____ increases
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increases; weight
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dispersion forces increase as molecular _____ increases
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size
This accounts for the higher melting and boiling points of larger alkanes |
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stereochemistry
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the branch of chemistry concerned with the three-dimensional aspects of molecules.
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conformations
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the different arrangements of atoms that result from bond rotation
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conformers
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(conformational isomers) -- molecules that have different arrangements
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Newman projection
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views the carbon-carbon bond directly end-on and represents the two carbon atoms by a circle
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The lowest-energy, most stable conformer is the one in which:
This is called what in a Newman projection? |
all six C-H bonds are as far away from one another as possible
Staggered when viewed end-on in a Newman projection |
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The highest-energy, least stable conformer is the one in which:
This is called what in a Newman projection? |
the six C-H bonds are as close as possible
Eclipsed in a Newman projection |
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The extra 12 kJ/mol of energy present in the eclipsed conformer of ethane is called:
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torsional strain
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Fill in the Newmans!
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anti conformation
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the lowest-energy arrangement
one in which the two methyl groups are as far apart as possible (e.g., in butane, 180 degrees away) |
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gauche conformation
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as a bond rotation continues, this energy minimum is reached at the staggered conformation where the methyl groups are 60 degrees apart
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steric strain
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the repulsive interaction that occurs when atoms are forced closer together than their atomic radii allow
result of trying to force two atoms to occupy the same space |
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Which is more stable?
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Make a graph of potential energy versus angle of bond rotation for propane, and assign values to the energy maxima
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natural gas
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primarily methane (but also contains ethane, propane, and butane)
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petroleum
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complex mixture of hydrocarbons
must be separated into fractions and then further refined before use |
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engine-knock
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an uncontrolled combustion that can occur in a hot engine
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octane number (of fuel)
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the measure by which its antiknock properties are judged
Straight chains have a higher tendency to knock e.g., heptane is terrible |
