Carboxylic Acids (alkanoic acids)
• Carboxylic acids contain a carbonyl group with an -OH
attached.
• The carboxyl functional group is -COOH:
O
R
OH
• Carboxylic acids are weak acids.
• Named like alkanes with “-oic acid” at the end.
• Typical carboxylic acids are found in spinach, vinegar,
cleaners, vitamin C, aspirin, and citrus fruits.
• Carboxylic acids are also used to make polymers for
fibers, paints, and films.
Reactions of Carboxylic Acids
1. Donate proton to a base (form alkanoate ion)
2. Esterification (squeeze play) – react with alcohol to form an
ester. Also referred to as condensation.
O
O
R
3.
OH
+
R'
HO
R'
R
+ H2O
O
3. Amide formation (also condensation) – react with amine to
form an amide.
O
O
H
R
OH
+
R'
N
H
R'
R
N
H
+ H2O
Esters
• Some common esters are: benzocaine (in sun burn
lotions), ethyl acetate (nail polish remover), vegetable
oils, polyester thread, and aspirin.
O
• Esters contain -COOR groups:
R
OR'
• Esters can be prepared by reacting a carboxylic acid with
an alcohol and eliminating water:
O
O
+ H2O
HO
CH
CH
+
2
3
C
C
H3C
OCH2CH3
H3C
OH
• Esters are named first using the alcohol part and then the
acid part (in the above example: ethyl from ethanol and
ethanoate from ethanoic acid).
• Esters tend to have characteristic odors and are used as
food flavorings and scents.
Amines
• Amines are organic bases.
• Just as alcohols can be thought of organic forms of water,
amines can be thought of organic forms of ammonia.
• Treat NH2 groups as substituents called “amino”
Examples
1.
1-aminobutane
NH 2
2.
NH2
NH2
1,6-diaminohexane
Amides
• Amides are composites of carbonyl and amine
O
functionalities:
C
R
N R'
H
• Named by longest chain followed by “anamide”
NH 2
Example:
propanamide
O
Nitriles
• Contain a cyanide group (CN)
• Named as alkane (full name) followed by “nitrile”
C
N
Example:
butanenitrile
• Halogenoalkanes (chloroalkanes, bromoalkanes) –
contain a halogen atom in place of a hydrogen. Halides
are treated as substituents
Examples
1.
3-chlorohexane
Cl
2.
3.
Br
2,3-dibromohexane
Br
Br
2-bromo-2-chloropropane
Cl
Reactions of halogenoalkanes – nucleophilic substitution
the “X” atom is replaced by a “nucleophile.”
• Nucleophile – something with an unshared pair of electrons
(attracted to a partially-positive carbon atom)
• Examples: OH-, NH3, CN-, R’-O, R’-NH2, H2O, etc.
• Hydroxide (OH-) is a better nucleophile than water (H2O),
since it is more attracted to the partially-positive carbon
atom.
Primary halogenoalkanes (contain only 1 carbon attached to
the carbon with the halogen atom) – react by a mechanism
called SN2 (heterolytic fission of the bond):
S = Substitution
N = Nucleophilic
2=
bimolecular
H
R
Nu:
C
H
H
X
Nu
C
R
+ X-
H
Curvy (curly) arrows indicate the movement of electrons.
Rate of SN2 depends on:
– concentrations of both reactants
– strength of nucleophile (CN- > OH- > NH3 > H2O)
– identity of halogen (bond strength)
• I is fastest and F is slowest
Tertiary halogenoalkane – SN1 reaction (heterolytic fission) – faster than SN1
1 = unimolecular (RDS) – rate depends only on the concentration of the
halogenoalkane
R
1.
R'
C
R
X
R'
R"
C+
+ X-
R"
Carbocation
R
R
2.
R'
C+
R"
:Nu
R'
C
R"
Nu
Examples – Write reactions for these nucleophilic
substitutions, using “curly arrows.”
1. Potassium cyanide +
H
H
C
C3H7
2. Ammonia +
Cl
Br
Elimination Reactions of Bromoalkanes
• Elimination of HBr molecule to form an alkene. Occurs in NaOH
in hot ethanol, heated under reflux. The H and Br are removed
from neighboring carbon atoms.
• E1 – unimolecular elimination reaction – a carbocation is
formed (similar to SN1), then the OH- removes the H:
H
H
H
H
C
C
H
Br
H
H
C
C
H
OH-
H
H
H
H
C
C
H
H
H
H
H
H
C
C
H