Chem&219 Unit 5 EXAM QUESTIONS AND ANSWERS
Generic formula for alcohols - CORRECT ANSWER-R-OH
phenol - CORRECT ANSWER-hydroxy-substituted aromatic molecules (any compound with an -OH
attached to a benzene ring)
IUPAC system rules for naming organic alcohols - CORRECT ANSWER-- organic alcoho...
Chem&219 Unit 5 EXAM QUESTIONS AND ANSWERS
Generic formula for alcohols - CORRECT ANSWER-R-OH
phenol - CORRECT ANSWER-hydroxy-substituted aromatic molecules (any compound with an -OH
attached to a benzene ring)
IUPAC system rules for naming organic alcohols - CORRECT ANSWER-- organic alcohols are named by
replacing the suffix of the parent chain of the molecule with the suffix -ol
- The parent chain is numbered so as to give the hydroxyl group the lowest possible number. (examples:
1-propanol, and cyclohexanol)
- with unsaturated alcohols the -ol suffix comes last and takes priority when numbering the parent chain
(2-propene-1-ol)
- Molecules with more than one -OH group get a prefix describing the number of -OH groups added to
the IUPAC name. (ethane-1,2-diol)
Molecules with more than one -OH group - CORRECT ANSWER-polyols
IUPAC rules for phenols - CORRECT ANSWER-- the suffix for an alcohol substituted benzene is "phenol"
- start the numbering at the OH group (so OH is at the 1 position)
Why can alcohols form strong hydrogen bonds? - CORRECT ANSWER-Due to the presence of the hydroxyl
group, as the O-H bond is highly polarized by the electronegative oxygen atom. This polarization places a
+ charge on the hydrogen atom and a - charge on the oxygen atom. The polarization in the O-H bond on
one alcohol molecule becomes attracted to the polarization in the O-H bond of another alcohol
molecule.
, Why do alcohols have much higher boiling points than other molecules of similar molecular weight? -
CORRECT ANSWER-hydrogen bonding between alcohol molecules
These attractions raise the amount of energy required to vaporize the liquid-phase molecules (boil),
which translates into increased boiling point temperatures.
Alcohol molecules can freely hydrogen bond to other molecules possessing what groups? - CORRECT
ANSWER-O-H, N-H, or S-H functional groupings
How does the water solubility of alcohol molecules change as the molecular weight changes? - CORRECT
ANSWER-Alcohol molecules of lower molecular weight are mostly soluble in water as a result of the
ability to hydrogen bond to OH, NH, or SH groups. As the molecular weight or carbon-chain length
increases, the alcohol molecules become correspondingly less soluble in water.
How do alcohols and phenols act as weak acids and weak bases? - CORRECT ANSWER-- acts as an acid by
donating the O-H proton as H
- acts as a base by accepting H+ using a lone pair on the O atom
amphoteric substances - CORRECT ANSWER-Substances that can act as both acids and bases (alcohols
and phenols)
Why is acid dissociation for most alcohols unfavorable (lies towards the left)? - CORRECT ANSWER-
Dissociation produces an alkoxide ion (the conjugate base of an alcohol), which is a very strong base.
How can you conduct acid-base reactions that favor the formation of weaker conjugate acids/bases? -
CORRECT ANSWER-To promote (favor) the formation of the alkoxide ion, the alcohol can be treated with
sodium or potassium metal (Na or K) or a base that is stronger than the RO- ion produced.
protonation of an alcohol - CORRECT ANSWER-When alcohols act as weak bases by using a lone pair on
the oxygen atom of the hydroxyl group, alcohols can accept a proton when they are placed in an acidic
environment.
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