Transcript Regents Unit 15b: Aldehydes, Ketones, Carboxylic Acids, & Esters

Hydrocarbon Derivatives
Aldehydes, Ketones, Carboxylic
Acids, & Esters
Carbonyl Group
• >CO
• Oxygen attached to a carbon by a double
covalent bond.
• Strong dipole
Aldehydes
O

• General formula: RCH or RCHO
• Carbonyl group is always at the end of the
aldehyde (C on one side, H on the other).
• Find the name of the alkane with the same
# of carbons. Change the final e to -al.
• Never need #’s for aldehydes – always at
end.
O
HCO H
H
=
H

HCH
Aldehyde comes from
Alcohol Dehydrogenated

O
HCH
Methanal
Common name =
formaldehyde
O

H
HCCH
H
Ethanal
= acetaldehyde
1 metabolic product of ethanol on its route
to acetic acid.
Acetaldehyde
• Evidence that it is carcinogenic.
• Natural component of many ripe fruits.
• Contributes to odors of rosemary, daffodil,
bitter orange, camphor, angelica, fennel,
mustard, & peppermint.
• A component of cigarette smoke.
CH3CH2CH2CHO
Ends in CHO so it’s
an aldehyde.
4 Carbons so base name is butane.
Drop final -e and add –al  butanal.
Properties of Aldehydes O
R
-
C=O
+

H
R
H
C=O
+
-
H
Aldehydes are polar! Bumps up the
boiling point.
1-way Hydrogen bonding in H2O.
Bumps up solubility.
+
H
Ketones
• Carbonyl group , >C=O, located within a C chain
instead of at the end.
• General Format:
=
O
RCR'
R and R' may or may not be the same.
Naming Ketones
•
•
•
•
•
Nearly always have a number.
Take the corresponding alkane name.
Drop final –e.
Add –one.
Number in front gives location of >C=O.
(Lowest possible #.)
=
H O H
HCCCH
H
H
2-propanone
Common name = acetone
=
O
CH3CH2CH2CCH3
2-pentanone
Aldehydes & Ketones
•
•
•
•
Known for appealing tastes & smells.
Used as flavorings in food & candy.
Used as fragrances in perfumes.
Vanilla & cinnamon = aldehydes
Properties of Aldehydes & Ketones
• Aldehydes & ketones contain C=O group,
which makes the molecules polar.
• Boiling point: Higher than alkanes, lower
than alcohols.
• In pure aldehydes & ketones, hydrogen
bonding does NOT occur. No H bonded to
O.
• Can have 1-way Hydrogen bonding in
water, so they are pretty soluble in H2O.
Carboxylic Acids
Acidic H+
=
O
• General Formula = RCOH
• Contains a carbonyl group & a hydroxyl
group bonded to same C.
• The H is acidic. It ionizes in water!
• Carboxylic Acids are electrolytes!
Ionization of Acetic Acid
CH3COOH + H2O  CH3COO- + H3O+
Table R
=
O
• General Format: R-C-OH or R-COOH
Which of the following is an
electrolyte?
A.
B.
C.
D.
CH3OH
alcohol
CH3COOH
aldehyde
CH2O
C 3H 6O
ketone
Correct answer is B, the carboxylic acid.
Which of the following is a
nonelectrolyte?
A.
B.
C.
D.
HCl
CH3COOH
NaOH
CH3OH
Correct answer is D, an alcohol.
Naming Carboxylic Acids
• Never need a number – functional group
always at end.
• Find name of corresponding hydrocarbon.
• Drop final –e.
• Add the ending –oic + the word acid.
=
O
HCOH
1 C  methane.
Methanoic acid
Sting in red ants, bees
O
=
H
HCCOH
H
2 C  ethane
Ethanoic Acid
or
Acetic acid
CH3CH2CH2CH2COOH
5 C’s  pentane so the name
is pentanoic acid.
Common carboxylic acids
• Acetic acid – vinegar. Also produced in
doughs leavened with a specific yeast 
sourdough bread
• Citric acid
• Tannic acid
• Ascorbic acid
• Lactic acid
– Poly(lactic acid) – biodegradable polymers
used as sutures in internal surgery.
Properties of Carboxylic Acids
• Contain –COOH group.
• H is bonded to O. Hydrogen bonding
occurs. Leads to increases in boiling point
over corresponding alkane.
• Also can form hydrogen bonds with water
so the smaller acids are pretty soluble.
Esters
=
O
• General format: RCOR‘
• R and R‘ = hydrocarbon branches. Can be the
same or different.
• Esters contain a carbonyl group and a bridge O,
both in the middle of the chain.
• Esters are POLAR, but NO H bonded to O
however.
Esters
=
O
• RCOR‘ or RCOOR’
• Combination of a carboxylic acid & an
alcohol.
• The carbonyl group and “R” come from the
carboxylic acid.
• The bridging O and the R’ come from the
alcohol.
Esters
• Responsible for many distinctive odors
•
•
•
•
•
Pineapple
Banana
Orange
Apple
Wintergreen
Naming Esters
• Name the hydrocarbon branch bonded to
the bridge O first. Branches end in –yl.
• The base name is derived from the branch
containing the carbonyl group. Count up
all the C atoms in this branch, including
the C in the carbonyl.
• Find the hydrocarbon base name. Drop
the final –e and add –oate.
=
O
CH3CH2COCH3
Carbonyl
Group
So you name this
branch 1st.
Bridge O
Methyl Propanoate
Bridge O
=
O
CH3CH2CH2COCH2CH3
Name this branch 1st.
Ethyl Butanoate
Pineapple
=
O
Bridge O
CH3COCH2CH2CH2CH2CH3
Name this branch 1st.
Pentyl Ethanoate
Banana
=
O
CH3OCCH2CH2CH3
Bridge O
Name this branch 1st.
4 C’s on the other side = but
Methyl butanoate - apple
O
=
CH3CH2CH2CH2CH2CH2CH2CH2-O-C-CH3
Bridge O
Name this branch 1st.
2 C’s on the other side: ethane
Octyl Ethanoate orange