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Why do low molecular weight alkanes have such low boiling points?
Only weak intermolecular van der Waal forces attract the molecules to each other; these forces are easily broken at low temperatures
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How many isomers of C6H14 are possible?
- 5 total
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What prefixes are used to describe alkane derivatives with alkyl chains of 8, 9, and 12 carbons?
8 = oct; 9 = non; 12 = dodec
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Why is the name 5-methylhexane incorrect?
The CH 3 (methyl) group would be at C-2 following the IUPAC rules, i.e. 2-methylhexane
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How many isomeric butyl substituents are possible?
Four: n-butyl; sec-butyl; isobutyl; t-butyl
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Give an alternate name for t-butylcycloheptane using the IUPAC form for the substituent
(1,1-dimethylethyl)cycloheptane
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Why do branched alkanes typically have lower boiling points than their unbranched isomers?
The branched substituents get in the way of the alkyl chains interacting and being attracted; less intermolecular interaction leads to a lower boiling point
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Why do alkanes not dissolve in water?
They are incompatible and do not attract; water is very polar, alkanes are very non-polar
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What oxidation numbers would you assign to the C atoms in CH3CH3, H2C=O, CH3Cl, and O=C=O?
- -3 in CH3CH3
- 0 in H2C=O
- -2 in CH3Cl
- +4 in CO2
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What type of valence orbitals are used by C in H2C=CH2 to form bonds?
C will use sp2 orbitals for sigma bonds and a p orbital for the pi bond
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What are the expected bond angles around each C atom in CH3CH=CH2?
109.5o around the C atom in CH3; 120o around the two C atoms in the double bond
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Provide the IUPAC name for CH3CH2CH2CH(CH3)CH(CH3)CH2CH3
3,4-Dimethylheptane
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Give the generic formula for an alkane
CnH2n+2
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Which would have the higher boiling point, heptane or 2-methylhexane?
Heptane; linear alkane with no branching interrupting intermolecular attractions
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Give an alternate name for the isopropyl substituent
(1-methylethyl)-
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What is wrong with the name 2-methyl-3-ethylnonane?
The ethyl should go before the methyl to keep the substituents correctly alphabetized
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Give the generic molecular formula for a cycloalkane
CnH2n
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What products are formed when any alkane is combusted?
CO2 and H2O
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Which molecule contains the most highly oxidized C atom, CH4, CH3OH, or CO2?
CO2 (+4)
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Which molecules contain the most unsaturation, alkenes, alkynes, or alkanes?
Alkynes (2 pi bonds)
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