Transcript Chemistry B11 Chapter 16,17 & 18 Amines, Aldehydes, Ketones and Carboxylic Acids Amines.

Chemistry B11
Chapter 16,17 & 18
Amines, Aldehydes, Ketones
and Carboxylic Acids
Amines
Amines
Amines:
• Are derivatives of ammonia NH3.
• Contain N attached to one or more alkyl (Aliphatic amine) or
aromatic groups (Aromatic amine).
-NH2 amino group
NH
CH22 CH3
CH3-NH2
CH3-NH-CH3
Ethylbenzene
Amines
Amines are classified into three groups:
depending on the number of carbon groups bonded to nitrogen.
CH3—NH2
CH3

CH3—NH
Primary 1°
Secondary 2°
CH3

CH3—N—CH3
Tertiary 3°
Naming Amines
IUPAC name – 1° amines
The same method as we did for alcohols.
- Drop the final “-e” of the parent alkane and replace it by “-amine”.
- Use a number to locate the amino group (-NH2) on the parent chain.
NH2
NH2
NH2
CH3-CH-CH3 NH2 CH3-CH-CH-CH3
2
4
3
1 CH3 CHCH31
2
Cl
3
2-Propanamine
Cyclohexanamine
2-propanamine
3-chloro-2-butanamine
H2 N
6
5
4
3
2
1
NH2
1,6-Hexanediamine
1,6-hexanediamine
Naming Amines
Common name
Names of alkyl groups (In alphabetical order) + “amine”
CH3—CH2—NH2
ethylamine
CH3—NH —CH3
dimethylamine
CH3
|
CH3—N—CH2—CH3
ethyldimethylamine
Aniline (common name)
NH
CH22 CH3
CH3
CH=CH
Aniline
Ethylbenzene
NH
CH22 CH3
2
1
3
4
Ethylbenzene
NO2
4-Nitroaniline
CH3
NH
CH22 CH3
CH=CH2
2
1
Toluene
Styrene
CH3 NH
CH22 CH3 CH=CH
1
2
3
3
CH3
4
CH3
Ethylbenzene
Toluene
Ethylbenzene
Styrene
Cl
Toluene
Styrene
3-Methylaniline
4-Chloro-3-methylaniline
Naming Amines
IUPAC name – 2° and 3° amines
– Take the largest group bonded to nitrogen as the parent amine.
– Name the smaller group(s) bonded to nitrogen, and show their locations
on nitrogen by using the prefix “N”.
NHCH3
N-Meth ylan ilin e
CH3
CH
NHCH
N
N
3
CH3
C
N,N -D imethylN,N -D imeth
N-Meth
ylan ilinaniline
e
cyclopentan amin e
cyclopentan a
CH3
CH3-N-CH2-CH3
N,N-Dimethylethanamine
Heterocyclic amines
When N is one of the atoms of a ring.
N
H
Pyrrolidine
CH3
H
Pyridine
Nicotine
Physical properties of Amines
1. They have unpleasant odors (rotting fish like ammonia).
2. They are polar compounds.
Difference in electronegativity between N - H (3.0 – 2.1 = 0.9)
3. 1° and 2° amines have hydrogen bonds (N-H).
Weaker than alcohols (O-H).
3° amines do not form hydrogen bonds (no H atom).
4. Boiling points: Hydrocarbons< Amines < Alcohols
5. Almost soluble in water (hydrogen bonding).
Chemical properties of Amines
They are weak bases (like ammonia): react with acids.
(to form water-soluble salts)
H
CH3
N..
H
+
..
H – ..
O–H
H
CH3
N
+
H
-...
. ..O – H
H
Some amines present in our blood and make it approximately basic (pH = 7.4).
Chemical properties of Amines
Aliphatic amines are weak bases by comparison with inorganic bases
such as NaOH, they are strong bases among organic compounds.
Aliphatic amines are stronger bases than aromatic amines.
(slightly stronger than NH3)
Clas s
Aliph atic
Ammonia
Aromatic
pKb
Example
3.0 - 4.0 CH3 CH2 NH2
N ame
Ethan amin e Stron ger bas e
4.74
8.5 - 9.5 C6 H5 NH2
Anilin e
Weaker base
Examples
Complete each acid-base reaction and name the salt formed.
(a) ( CH3 CH2 ) 2 NH + HCl
+ CH3 COOH
(b )
N
Examples
Complete each acid-base reaction and name the salt formed.
Solutions:
(a) (CH3 CH2 ) 2 NH + HCl
+
-
(CH3 CH2 ) 2 NH2 Cl
D ieth ylammoniu m
chloride
-
+ CH3 COOH
(b)
N
CH3 COO
N+
H
Pyridinium acetate
Aldehydes
Ketones
Carbonyl group
O
C
Aldehydes
Ketones
Carboxylic acids
Esters
O
CH3 COCH2 CH3+ N aOH
Eth yl ace tate
H
h
S odiu m
h ydroxide
Aldehydes and Ketones
O
• In an aldehyde, at
least one H atom is
attached to a
carbonyl group.
• In a ketone, two
carbon groups are
attached to a
carbonyl group.
C
Naming Aldehydes
Step 1
Select the longest carbon chain
that contains the carbonyl group (C=O).
Step 2
Number from the end nearest C=O group.
Step 3
Change the ending of parent alkane from -e to -al.
No number for carbonyl group C=O (it always comes first).
Step 4
Give the location and name of each substituent
(alphabetical order) as a prefix to the name of the
main chain.
Naming Aldehydes
• Common names for the first two aldehydes use the prefixes “form” (1C)
and “acet” (2C) followed by “aldehyde”.
O
║
H─C─H
methanal
(formaldehyde)
O
║
CH3─ C ─H
ethanal
(acetaldehyde)
O
║
CH3─CH2─ C ─H
propanal
O
║
CH3─CH─CH2─ C─H
CH3
4
3
2
1
O
║
Cl─CH2─CH2─ C─H
3
2
3-Methylbutanal
1
3-chloropropanal
Naming Ketones
Step 1
Select the longest carbon chain
that contains the carbonyl group (C=O).
Step 2
Number from the end nearest C=O group.
Step 3
Change the ending of parent alkane from -e to -one.
Use the number to show the location of C=O.
Step 4
Give the location and name of each substituent
(alphabetical order) as a prefix to the name of the
main chain.
Naming Ketones
• In the common name, name the “alkyl groups” alphabetically attached
to the carbonyl group and add the word “ketone”.
O
║
CH3 ─ C ─CH3
O
║
CH3─C─CH2─CH3
1
propanone
(dimethyl ketone)
2
3
4
2-butanone
(ethyl methyl ketone)
e
O O
O C
1
O1 22
5
3
2 Cl 4
2
1
H
+ O2
O
2
Be nz al de hyde
2-Methylcycloh
exanone
2-Methylcycloh exanone
5-Meth yl-3-h exanone
2
2
Be nz oi c acid
2-Methylcycloh exanone
2
O
O
O
3
4
5
6
5-Meth yl-3-h exanone
+ O2
OH
O
1
H
3-Chloro Be nz al de hyde
1
6
O
C
O
C
Acetone
1
2
3
4
5
1
6
2
5-Meth
yl-3-h exanone
2-Methylcycloh exanone
2-Meth
O
5
6
O
2
1
H
lbutan al
al
3
O
O
3
1
O2
H
3
1
2
Hexanal
H
2-Prop enal
(Acrolein)
4
4
2
3
1
2
H
2-Prop enal
(Acrolein)
H
3-Methylbutan al
OH O
4
5
3
4
3
1
1
1
3-Hydroxy-4-meth
ylp
entanal
6
4 3 2
H
3-Hydroxy-4-meth ylp entanal
NH2
3-Amino-4-ethyl-2-h exanone
O
OH O
5
4
3
H
O
OH O
5
1
1
H
O
1 ylp entanal
3-Hydroxy-4-meth
6
4 3 2
NH2
3-Amino-4-ethyl-2-h exanone
6
4
3
2
1
NH2
3-Amino-4-ethyl-2-h exanone
3-A
Physical properties of Aldehydes and Ketones
1. They have strong odors (ketones have pleasant odors).
δ-
2. They are polar compounds.
C-O
δ+
3.5-2.5 = 1
3. Only dipole-dipole interactions (no hydrogen bonding).
4. Low boiling points compare to amines and alcohols.
Higher than hydrocarbons.
H
5. Soluble in water (no soluble in nonpolar compounds).
δ-
Hydrogen bond with water.
δ+
δ+
H
O
Chemical properties of Aldehydes and Ketones
1. Oxidation: only for aldehydes (not for ketones).
O
O
CH3─CH2─CH2─CH2─C─H
=
=
K2Cr2O7
CH3─CH2─CH2─CH2─C─OH
H2SO4
Pentanal
Pentanoic acid
K2Cr2O7: Oxidizing agent
Liquid aldehydes
are sensetive to oxidation.
O
C
2
H
O
C
+ O2
2
OH
No oxidizing agent
Be nz al de hyde
Be nz oi c acid
Chemical properties of Aldehydes and Ketones
2. Reduction:
Like reducing the alkene (C = C) to alkane (C – C):
– Reduction of an aldehyde gives a primary alcohol (-CH2OH).
– Reduction of a ketone gives a secondary alcohol (-CHOH-).
=
O
+ H2
Pentanal
1-Pen tan ol
=
O
CH3─C─CH2─CH3
2-butanone
CH3─CH2─CH2─CH2─CH2─ OH
+ H
2
tran si ti o n
m etal catal y st
OH
-
CH3─CH2─CH2─CH2─C─ H
tran si ti on
metal cataly st
CH3─CH─CH2─CH3
2-butanol
Chemical properties of Aldehydes and Ketones
Sodium borohydride: produces hydride ion: H-
NaBH4
Reducing agent
Reduction mechanism:
H :-
+
C O
H
C O
-
H3 O +
H
C O-H
Hydride
ion
O
NaBH4
OH
+
H3 O
O-H
H
Carboxylic Acids
Carboxylic Acids
A carboxylic acid contains a carboxyl group, which is a
carbonyl group attach to a hydroxyl group.
carbonyl
group
O

CH3 — C—OH hydroxyl group or CH3COOH
carboxyl group
CH3CO2H
Naming Carboxylic Acids
• In the IUPAC name of carboxylic acids, the “-e” in the
name of the longest chain is replaced by “-oic acid”.
• The common names use prefixes “form-” and “acet-” for the first
two carboxylic acids.
H-COOH
CH3-COOH
methanoic acid
ethanoic acid
CH3-CH2-COOH
formic acid
acetic acid
propanoic acid
CH3-CH2-CH2-COOH butanoic acid
Naming Carboxylic Acids
– Number the chain beginning with the carbon of the carboxyl group.
– Because the carboxyl carbon is understood to be carbon 1, there is no
need to give it a number.
CH2 – CH3
CH3
1
3
2
1
CH3─CH─CH2─COOH
CH3─CH2─CH─COOH
3-Methylbutanoic acid
2-Ethylbutanoic acid
OH
5
O
1
OH
5-Hydroxylhexanoic acid
H2 N
4
1
COOH
4-Aminobenzoic acid
Naming Dicarboxylic Acids
– Add the suffix “-dioic acid” to the name of the parent alkane that
contains both carboxyl groups; thus, “-ane” becomes “-anedioic acid”.
– The numbers of the carboxyl carbons are not indicated because they
can be only at the ends of the chain.
O
HO
O
1
2
3
OH
HO
O
1
OH
O
Ehanedioic acid
O
HO
4
O
5
1
OH
HO
Propanedioic acid
O
O
1
OH
6
O
O
Butanedioic acid
HO
1
Pentanedioic acid
Hexanedioic acid
OH
Physical properties of Carboxylic Acids
1- The carboxyl group contains three polar covalent bonds;
C=O, C-O, and O-H. So they are so polar.
2- Carboxylic acids have higher boiling points than other types of organic
compounds (with the same molecular weight) because of hydrogen bonding.
Hydrogen bonding
between two molecules
H3 C
dO
d+
H O
C
C
O
H
d+
CH3
O
d-
3- They are more soluble in water than alcohols, ethers, aldehydes, and
ketones because of stronger hydrogen bonding.
4- Liquid carboxylic acids have sharp and disagreeable odors.
5- They taste sour (exist in pickle, lime, and lemon).
Fatty Acids
• Long, unbranched chain carboxylic acids and they are found in animal
fats, vegetable oils, or phospholipids of biological membranes.
COOH S te aric acid (18:0)
(mp 70°C )
•
COOH O l e ic acid (18;1)
Most have between 12 and 20 carbons in an unbranched chain.
(mp 16°C )
• In most unsaturated fatty acids, the cis isomer is usually
existed
and
the
COOH Lin
ol
e
ic
acid
COOH S te aric acid (18:0) (18:2)
trans isomer is rare.
(mp-5°C )
(mp 70°C )
COOHCOOH
O l e icLin
acid
ol e(18;1)
ni c aci d (18:3
(mp Cis
16°C
) -11°C )
(mp
•
COOH Lin ol e ic acid (18:2)
Unsaturated fatty acids have lower melting points than their
saturated
(mp-5°C
)
counterparts.
COOH Lin ol e ni c aci d (18:3)
Fatty Acids
Saturated fatty acids are solids at room temperature.
Packed together  Maximum London dispersion forces
COOH
COOH
COOH
COOH
COOH
Fatty Acids
Unsaturated fatty acids are liquids at room temperature.
Can not packed together  London dispersion forces
COOH
COOH
Cis
COOH
COOH
COOH
Esters
In an ester, the H in the
carboxyl group is replaced
by an alkyl group.
O

CH3 — C—O —CH3
ester group
Soaps
• Natural soaps are sodium or potassium salts of fatty acids.
• They are prepared from a blend of tallow and coconut oils
(triglycerides).
CH2 – CH – CH2
OH
• Triglycerides are triesters of glycerol.
OH
OH
1,2,3-Propanetriol
(glycerol, glycerin)
• the solid fats are melted with steam and the water insoluble
triglyceride layer that forms on the top is removed.
Soaps
• Preparation of soaps begins by boiling the triglycerides with
NaOH. The reaction that takes place is called saponification.
• Boiling with KOH gives a potassium soap.
O
O
CH2 OH
O
O CH2 OCR
saponification
+
CH2 OH +
CH2 OCR+ 3 N aOH
O
O
3
RCO
N
a
CHOH
RCOCH
saponification
+
O +
+
3
N
aOH
3
RCO
N
a
CHOH
RCOCH
O
CH2 OH
CH2 OCR
CH2 OHetriol S odiu m soaps
1,2,3-Propan
A triglCH
yce
ri de
2 OCR
1,2,3-Propan
etriol
(Glyce
rol; gl yce
rin )S odiu m soaps
de rol )
( a triAe trigl
ste r yce
of glriyce
(Glyce rol; gl yce rin )
( a tri e ste r of gl yce rol )
Soaps
Hydrophobic part: nonpolar
Hydrophilic part: polar (remains in contact with environment)
O
+
3 RCO N a
riol S odiu m soaps
e rin )
Soaps
When soap is mixed with dirt (grease, oil, and …), soap
micelles “dissolve” these nonpolar, water-insoluble molecules.
Chemical properties of Carboxylic Acids
1- They are weak acids.
Substituents of high electronegativity, especially -OH, -Cl, and -NH3+, near
the carboxyl group increase the acidity of carboxylic acids.
2- Reaction with bases:
They react with NaOH, KOH, NH3, and other strong bases to form watersoluble salts.
COOH
+
NaOH
H2 O
Ben zoic acid
(slightly soluble in water)
COOH + NH3
Benzoic acid
+
COO Na + H2 O
Sodium b enzoate
(60 g/100 mL water)
H2 O
-
COO NH4
+
Ammoniu m b enzoate
Chemical properties of Carboxylic Acids
3- Fischer Esterification:
- A carboxylic acid reacts with an alcohols to form an ester.
- Using an acid catalyst such as concentrated sulfuric acid.
O
H2 SO4
CH3 C-OH + H-OCH2 CH3
Ethanoic acid
Ethanol
(Acetic acid) (Ethyl alcohol)
O
CH3 COCH2 CH3 + H2 O
Ethyl ethanoate
(Ethyl acetate)
The best way to prepare an ester.