Chem&219 Unit 5 Exam Questions and Answers Grade
A+
Generic formula for alcohols - Answer-R-OH
phenol - Answer-hydroxy-substituted aromatic molecules (any compound with an
-OH attached to a benzene ring)
IUPAC system rules for naming organic alcohols - 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 - Answer-polyols
IUPAC rules for phenols - Answer-- the suffix for an alcohol substituted benzene is
"phenol"
- start the numbering at the OH group (so OH is at the 1 position)
(examples: phenol, 3-methylphenol, 2,4-dinitrophenol)
, Why can alcohols form strong hydrogen bonds? - 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? - 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? - Answer-O-H, N-H, or S-H functional groupings
How does the water solubility of alcohol molecules change as the molecular
weight changes? - 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? - 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 - 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)? -
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? - Answer-To promote (favor) the formation of the alkoxide
A+
Generic formula for alcohols - Answer-R-OH
phenol - Answer-hydroxy-substituted aromatic molecules (any compound with an
-OH attached to a benzene ring)
IUPAC system rules for naming organic alcohols - 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 - Answer-polyols
IUPAC rules for phenols - Answer-- the suffix for an alcohol substituted benzene is
"phenol"
- start the numbering at the OH group (so OH is at the 1 position)
(examples: phenol, 3-methylphenol, 2,4-dinitrophenol)
, Why can alcohols form strong hydrogen bonds? - 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? - 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? - Answer-O-H, N-H, or S-H functional groupings
How does the water solubility of alcohol molecules change as the molecular
weight changes? - 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? - 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 - 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)? -
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? - Answer-To promote (favor) the formation of the alkoxide
