organic chemistry: carbonyl compounds and nitrogen compounds
DESCRIPTION
Organic Chemistry: Carbonyl Compounds and Nitrogen Compounds Discussing nucleophilic addition on carbonyl discussion and reactions on carboxylic acid and its derivates. Also a brief description about amino acids and protein structuresTRANSCRIPT
Organic Chemistry III
Carbonyl compounds and
Nitrogen Compounds
Indra Yudhipratama
Outline Carbonyl Compounds
(Aldehydes and Ketones) Reduction-oxidation
reactions Addition reaction Identification Reaction
Carboxylic Acid and Derivatives The Acidity of Carboxylic
acid The Formation Reaction to form salts, esters,
and acyl chloride Nitrogen Compounds
The basicity of amines Amino acids and Proteins
Aldehydes and Ketones The Formation and the redox of Aldehydes and Ketones
R
R
O
R
O
H
N a B H 4
N a B H 4
C r 2 O 72 -
H +
C r 2 O 72 -
H +
C r 2 O 72 -
H +
C r 2 O 72 -
H +
CH3
O
OH
butanoic acid
No Reaction
CH3 OH CH3 O
CH3
CH3
OH
CH3
CH3
O
Aldehydes and Ketones The Nucleophilic Addition
Nucleophile is a chemical that can donate a pair of electron with the subsequent formation of a covalent bond
Nucloephilic Addition is addition reaction in which the first step is the attack by a nucleophile on the electron-deficient part of molecule
R
O
R
Aldehydes and Ketones E.g. Reaction between NaCN in water with butanal
via:
Draw the product of this reaction:
H
ONaCN, HCN
H
NC OH
cyanohydrin
H
O
CN
H
O CN H CN
H
HO CN
O
NaCN, HCN
NH
NO2
NO2
R
O
R'
H2N
NH
NO2
NO2
N
R
R'
Aldehydes and Ketones Reaction with 2,4-DNPH (2,4-dinitrophenylhydrazine) – Identification.
Gives the yellow precipitate of hydrazone. To identify the carbonyl groups
2,4-DNPH Hydrazone
Aldehydes and Ketones
Another identification test Fehling’s Reagent (an alkaline solution of Cu2+ ions
complex) Aldehydes: Red precipitate and carboxylic acid forms. Ketones: No changing
Tollen’s Reagent (an aqueous solution of AgNO3 in excess ammonia) Aldehydes: Silver mirror and carboxylic acid forms. Ketones: No changing
Aldehydes and Ketones
Another identification test Acidified Cr2O7
2-
Aldehydes: The solution turns green (Cr3+) Ketones: No changing (solution still yellow-orange)
An alkaline solution of iodine To identify CH3CO- FG
OI2
NaOH(aq)I3C
OI2
NaOH(aq)O
O
+ CHI3
Aldehydes and Ketones(Summary of Identification)
Type of Test Aldehydes Ketones
2,4-DNPH (+) yellow ppt. (+) yellow ppt.
Tollen’s Reagent (+) silver mirror (-) no changing
Fehling’s Reagent (+) red ppt. (-) no changing
Oxidation acidified Cr2O7
2-
(+) solution turns into green
(-) no changing
An aqueos alkaline of iodine to identify CH3CO – gives yellow ppt.
Carboxylic Acids Main features: Behaves as an acid and has the highest b.p. along all
the functional group. The formation of Carboxylic acid
Oxidation of alcohol
R
OH
O
CH3
O
OH
butanoic acid
CH3 OH
CH3 O
C r 2 O 72 -
H +
C r 2 O 72 -
H +
Carboxylic acids
Hydrolysis cyanohidrin or nitriles
Via:Ph
NH
OH2 Ph
NH
H2O
Ph
OH
NH
H
- H++ H+
Ph
OH
NH2Ph
O
NH2
H
Ph
O
NH2H3O+
Ph
O
OH
Hydrolysis amide (see later)
Ph CN
H2O, H2SO4
Ph
OH
O
Carboxylic AcidsThe Acidity of Carboxylic Acids Acidity How strong the acid is. The easiness to release H+ (proton) Measures as Ka or pKa [pKa = -log(Ka)]. Higher pKa, weaker the acid
FG substituted carboxylic acid e- withdrawing FG (e.g. Cl) stabilise the ion by inductive effects. More e- with drawing FG more stable the ion. Further the FG, decrease the acidity. e- donating FG un-stabilise the ion, so the acidity is decreasing.
CH3
OH
O
+ OH2 O+
H
H
H
+CH3
O
O
-
Carboxylic Acids
(pKa = 4.76) (pKa = 2.86) (pKa = 1.48) (pKa = 0.70)
(pKa = 4.81) (pKa = 2.85) (pKa = 4.05) (pKa = 4.50)
CH3
OH
O
OH
OCl
OH
OCl
Cl OH
OCl
Cl Cl
OH
O
CH3
Cl
OH
O
CH3
Cl
OH
O
ClOH
O
CH3
Carboxylic AcidsQuick Review:
Predict the order of acidity from the strongest to the weakest from those acids below. Give your reason.
(1) (2) (3) (4)
Ans:
(1) > (2) > (3) > (4)
F has the highest electronegativity, so it has the biggest inductive effect/the electrons more attracts toward FG. Thus, the resonance is more stabilised compare to the others.
OH
O
ClOH
O
FOH
O
BrOH
O
I
fluoroacetic acid chloroacetic acid bromoacetic acid iodoacetic acid
Carboxylic Acids The Reactions
Formation of Salts Reacts with an alkaline solution to give salts.
Reacts with alcohols to form esters
Reaction with SOCl2 or PCl3 or PCl5 to form acyl chlorides
R
OH
O
+ NaOH R
O-
O
+ OH2
Na+
R
O
OH
R' OH+H3O+
R
O
O
R'
R
O
OH R
O
Cl
SOCl2 or
PCl3 orPCl5
Carboxylic Acid Derivatives Ester Formation under acidic condition
Via:
Esters can also be synthesised by reacting acyl chlorides with alcohol. Why can’t we make esters under alkaline condition?
O
OH
Et OH+H3O+ O
O
Et
O
OH
Et OH
OH2H
O
OH
H
O
O OH
Et
H
OH2H
O
O HO
Et
H
H
O
O HO
Et
H
HO
O
Et
H H2O
O
O
Et
Carboxylic Acid Derivates Quick Quiz
Predict the results of the reaction below. All reactions are in acidic condition.
H OH
On-BuOH
H3O+
OH
O
OH
MeOH
H3O+
H O
O
O
O
OH
Carboxylic Acid Derivates
Ester hydrolysis with acid catalyst
Via:
O
OH
Et OH+H3O+
O
O
Et
O
O
Et
H OH2 O
O
Et
H
H2O
O
HO OH
H
H2O
O
HO OH
EtEt
H OH2
O
OH
Et OH+
O
Et
HO OH
H
HH2O
O
OH
+ OH3
Carboxylic Acid Derivates
Ester hydrolysis in alkaline condition
Via:
This process is also called saponification (making soap)
O
O
Et OH+O
O
Et
NaOH(aq)
Na
O
O
Et
OH
O
O OH
EtO
O
HO Et
O
O
Et OH+
Carboxylic acid Derivates Mainly, Polyesters can be formed by reacting dicarboxylic acids and
diols
OH
OO
OH
OH
OH
+
benzene-1,4-dicarboxylic acid
ethane-1,2-diol PET
Carboxylic Acid Derivates Acyl Chloride
The hydrolysis would give carboxylic acids. Reacts readily with water
R
OH
O R
Cl
OS O C l2 o r P C l3 o r
P C l5
R
Cl
O H 2 OR
OH
O
O H -/H2 O
R
O-
O
Carboxylic Acid Derivates The reactions of acyl chloride
Reacts with alcohols to give esters Reacts with primary amines to give amides
Via:
O
Cl
HNMe2
O
N
O
Cl
HN
N
O Cl
HHN N
O Cl
N
O
+ Me2NCl
Carboxylic acid derivates
Reacts with phenol to give esters
Via:
O
Cl
PhOHO
OPhbase
O
Cl
OH
O
O
O
H
O Cl
BO
O Cl
OPh
PhOH
Nitrogen Compounds Main Features
Relatively high b.p. for organic compounds High solubility in water and polar solvent Act as basic compounds
NH3 NH2 RNH R
R1N R
R1
R2ammonia
NH3 NH2 CH3 NH CH3
CH3 N CH3
CH3
CH3ammonia methanamine N-methylmethanamine N,N-dimethylmethanamine
The Classification
1o 2o 3o
e.g.
Nitrogen Compounds The formations
Substitution reaction
Reduction of nitrile
CH3
Br
N H 3 CH3
NH2
CH3
N
L iA lH 4
D ry e th e r
CH3
NH2
Nitrogen Compounds The reactions
The formation of Amides from amines and acyl chlorides
Why amides can’t be formed from reaction of carboxylic acids and amines?
O
Cl
HNMe2
O
N
OH
O
+HN
N
O
Nitrogen Compounds The Hydrolysis in aqueous alkaline solution
Via:
Requires stronger (more extreme) condition than hydrolysis of ester
NH
Oconc. NaOH
O
O
Na+ H2N
NH
O
HN
OH
NH
O OH
O
O
HO
O
H2N
Nitrogen Compounds The Hydrolysis in aqueous acidic solution
Via:NH
Oconc. H2SO4
3 hrs, 100 oC OH
O
+ H3N
NH
O
H
NH
O
H
H2O
NH
HO OH
H
NH
HO OHH
HN
HO OH
H
OH
O
HO
OH
H2N H3N
H
Nitrogen Compounds The formation of Polyamides
It is formed from diacyl chlorides and diamines
Cl
OO
Cl
NH2NH2+
28-4 Proteins
Zwitterion
Copyright © 2011 Pearson Canada Inc.
General Chemistry: Chapter 28Slide 33 of 59
Peptides
The peptide-bond structures
The character of double bond at peptide bond create atoms C, N, H, O almost co-planar.
Protein 20 different amino acids
polymerise to build protein. Protein has unique sequence. The sequence of amino acids
that build the protein is called primary structure.
Different sequences, provide different function of protein
Primary structure of myoglobin
From Gene to Protein (Protein Synthesis in vivo)
The Genetic Code
Translasi
Secondary Structure
Stabilise by hydrogen bonding
Tertiary Structure
Two Main structure:
Fibrous and Globular
Linkages contributing to tertiary structure of proteins
FIGURE 28-15
The four levels of protein structureFIGURE 28-16
Copyright © 2011 Pearson Canada Inc.
General Chemistry: Chapter 28Slide 43 of 59
Another example of quaternary structure:
Nucleosome