Chapter 5 Flashcards
Alcohol functional group
-OH
hydroxyl group
Alcohol suffix
-ol
Phenols
Aromatic alcohols = Hydroxyl groups attached to aromatic rings
Ortho or o prefix
2 functional groups are on adjacent carbons in a ring
Meta or m prefix
2 functional groups are separated by 1 Carbon on a ring
Para or p prefix
2 functional groups are in opposite sides of a ring
alkoxide ions
the conjugate base to an alcohol
an ion with an organic group bonded to a negatively charged oxygen atom
the hydroxyl hydrogen is weakly ______ (acidic/basic)
acidic
alcohols can dissociate into ___________
protons and alkoxide ions
Key physical property of alcohol
High melting points due to hydrogen bonding of OH Groups
hydroxyl hydrogens of phenols are ______ acidic than other alcohols
more
are alcohols soluble in water? why?
yes if there is a relatively small hydrophobic alkyl group; the hydrophilic hydroxyl group can hydrogen bond with the water
no if there is a large hydrophobic alkyl group
Electron withdrawing substituents ____ acidity
Increase
Electron donating substituents ____ acidity
Decrease
More alkyl groups on non aromatic alcohols = _____ acidic
Less acidic
Bc alkyl groups destabilize negative charge
More substituted carbocations have _____ stability
Higher
Bc alkyl groups help stabilize positive charges
Why are phenols more acidic than other alcohols
Possible Resonance between the ring and the lone pairs of the oxygen in the OH group
3 main reactions involving alcohols
Oxidation, preparation of mesylates and tosylates, and protection of carbonyls
primary alcohol
the carbon atom of the hydroxyl group (OH) is attached to only one single alkyl group
secondary alcohol
the carbon atom of the hydroxyl group (OH) is attached to two other alkyl groups (and one hydrogen)
tertiary alcohol
the carbon atom of the hydroxyl group (OH) is attached to three other alkyl groups (no hydrogens)
diol
an alcohol with 2 OH groups
if you oxidize a primary alcohol one time you will get a ______
aldehyde
if you oxidize a primary alcohol TWICE you will get a ______
carboxylic acid
(because oxidation of an aldehyde results in a carboxylic acid)
if you oxidize a secondary alcohol ONCE you will get a ______
ketone
if you oxidize a tertiary alcohol ONCE you will get ______
NO REACTION! under normal conditions…
(there needs to be an alpha hydrogen to oxidize the species)
oxidation involves an ______ in oxidation state
increase
chromic acid
2 ways chromic acid is generated in solution
the jones reagent: sodium dichromate + sulphuric acid + water → chromic acid
chromium trioxide + h3o+ + acetone → chromic acid
describe the mechanism of alcohol oxidation (using chromic acid)
the hydroxyl hydrogen and chromic acid OH combine to form water
a chromate ester intermediate is formed
a base (water) picks up the alpha hydrogen from the alcohol, forming a double bond between the hydroxyl carbon and oxygen and kicking off the chromium atom
during alcohol oxidation, what happens to the oxidation state of chromium?
it is reduced from Cr6+ (orange-ish) to Cr3+ (green-ish)
what reagent should be used to oxidize a primary alcohol just ONCE to form an aldehyde but not carboxylic acid
pyridinium chlorochromate (PCC)
(milder reagent than the jones reagent)
which reagents could be used to oxidize a secondary alcohol to a ketone?
jones reagent OR PCC
