Ch. 8: Carboxylic Acids Flashcards
defn: carboxylic acid
contains both a carbonyl group and a hydroxyl group, bonded to the same carbon
are carboxylic acids terminal groups?
always!
how are carboxylic acids named?
by adding the suffix -oic acid to the parent root when the carboxylic acid is the highest-priority functional group
the carbonyl C becomes C #1
how are cyclic carboxylic acids named?
by listing the cycloalkane with the suffix carboxylic acid
how are salts of carboxylic acids named?
beginning with the cation, followed by the name of the acid with the ending -oate replacing -oic acid
defn: dicarboxylic acids
have a carboxylic acid group on each end of the molecule
what is the smallest dicarboxylic acid?
oxalic acid (2 carbons)
what are the next 5 straight-chain dicarboxylic acids?
what suffix do their IUPAC names have?
malonic
succinic
glutaric
adipic
pimelic
acids
suffix: -dioic acid
what are the physical properties of carboxylic acids?
- many are similar to those of aldehydes and ketones because they both contain carbonyl groups
- however, the additional hydroxyl group permits carboxylic acids to hydrogen bond and provides another acidic hydrogen that can participate in reactions
why are carboxylic adis polar?
because they contain a carbonyl group
why can carboxylic acids form hydrogen bonds?
because they contain a hydrogen bonded to a very electronegative atom
why do carboxylic acids display particularly strong intermolecular interactions?
because both the hydroxyl oxygen and carbonyl oxygen can participate in hydrogen bonding
what is a result of the fact that carboxylic acids display strong intermolecular interactions?
they tend to form dimers
defn: dimers
pairs of molecules connected by two hydrogen bonds
why do carboxylic acids have elevated boiling points and melting points compared to corresponding alcohols? (2)
multiple hydrogen bonds AND increasing molecular weight
what causes a very stable carboxylate anion? (3)
- the hydroxyl hydrogen of a carboxylic acid is quite acidic
- thus there is a negative charge that remains after the H is removed and resonance stabilization occurs between both of the electronegative O atoms
- delocalization of the negative charge causes a very stable carboxylate anion
what things contribute to the acidity of a carboxylic acid and how?
- the more stable the conjugate base is, the easier it is for the proton to leave, thus the stronger the acid –> carboxylic acids are relatively acidic
- substituents on carbon atoms near a carboxyl group influence anion stability and therefore affect acidity
give 2 examples of electron-withdrawing groups and electron-donating groups. what affect do each of these types of groups have?
electron-withdrawing = -NO2, halides –> increase acidity
electron-donating: -NH2, -OCH3 = destabilize the negative charge, decreasing the acidity
how does the proximity to the carboxyl group of the substituent groups that are electron-withdrawing or electron-donating affect their impact?
the closer they are, the greater the effect
in dicarboxylic acids, does each -COOH group influence each other?
yes
why are carboxylic acids electron-withdrawing?
due to the electronegative oxygen atoms they contain
what is the net result of the fact that the -COOH groups in dicarboxylic acids influence each other and the fact that carboxylic acids are electron-withdrawing?
dicarboxylic acids are more acidic than the analogous monocarboxylic acids
when one proton is removed from a dicarboxylic acid, and the carboxylate anion is formed, how is acidity impacted?
there is an immediate decrease in the acidity of the remaining carboxylic acid
why is the second proton of the carboxylate anion (previously dicarboxylic acid) harder to remove than the analogous proton of a monocarboxylic acid?
harder to remove - less acidic
if the second group were deprotonated on the carboxylate anion, it would create a doubly charged species with two negative charges repellinge ach other