organic chemistry 212 organic chemistry 212
10/13/2009
ORGANIC CHEMISTRY 212 Lecture 13: October 13th, 2009
Youla S. TSANTRIZOS Office: Chemistry Department Pulp & Paper, Room 108 Email: [email protected]
ORGANIC CHEMISTRY 212 Chapter 7 and 8: ALKENES - the E / Z naming system - Synthesis via Elimination reactions - Hydrogenation - Addiotion of Halogenation
1
10/13/2009
Molecular Structure of Ethene (C2H4)
~ 118o ~ 121o
1
1
2s
2
3
2p
sp2
sp2
2p
+
~ 121o
Molecular Structure of Ethene (C2H4)
~ 118o ~ 121o
π H
H
H
H
σ
2
10/13/2009
Ethene (Ethylene): a Plant Hormone
Ethene (Ethylene): a Plant Hormone Photosynthesis
Glu
Glu Biosynthesis of Anthocyanins Requires the Sugar Glucose
3
10/13/2009
Reaction of Cyclopentanol with CH3CO2H H _ Br
Br -
Reaction of Cyclopentanol with CH3CO2H H _ Br
Br -
Dehydration of secondary or tertiary alcohols usually proceed via E1 elimination The stability of the carbocation is a key factor in this reaction!
4
10/13/2009
Effects of Substituents on Dehydration H
1o
OH
1o
2o
3o
H H Increasing Reactivity towards a SN1 Substitution Reaction
Increasing Reactivity towards an E1 Elimination Reaction
Dehydration Requires Acidic Conditions ! H
1o
OH
1o
2o
3o
H H
HBr
Na+ BrNO REACTION !
5
10/13/2009
Hydrogenation Reaction of Alkenes H2 metal catalyst Pd (Palladium) or Ni (Nickel) or Rh (Rhodium)
Period Table
6
10/13/2009
Hydrogenation Reaction of Alkenes
H
H
H
H
Relative Heat of Hydrogenation of Alkenes
E N T H A L P Y ∆Ho = -127 kJ/mol
∆Ho = -120 kJ/mol
∆Ho = -115 kJ/mol
CH3CH2CH2CH3 • All reactions are exothermic, the ∆Ho is the heat of reaction • All reactions require H2 and a metal catalyst • Product from all reactions is butane
7
10/13/2009
Relative Stability of Alkenes
INCREASING STABILITY
• the greater the substitution (i.e. number of attached alkyl groups) the more stable the alkene • trans-double bonds are more stable than cis, except in ring systems with less than 6 carbons
Cycloalkenes
trans-cyclohexene - evidence that it forms as a very high energy reactive intermediate NOT stable at room temperature!
8
10/13/2009
The Health Effects of trans-Double Bonds
Unsaturated fats (oils) Molecules with cis-double bonds
Essential starting materials for the Biosynthesis of hormones
Saturated fats (animal fat, butter) Molecules with NO bonds
Increase the risk of cardiovascular disease associated with high levels of cholesterol
The Health Effects of trans-Double Bonds Comparative properties of common cooking fats (per 100g) Total Fat
Saturated Fat
Monounsaturated Fat
Polyunsaturated Fat
Protein
Butter
81g
51g
21g
3g
1g
Vegetable Shortening (hydrogenated)
71g
23g
8g
37g
0g
Olive Oil
100g
14g
73g
11g
0g
Lard
100g
39g
45g
11g
0g
9
10/13/2009
The Health Effects of trans-Double Bonds The process of making margarine Vegetable oils (usually liquids) are partly hydrogenated to convert them to solid fats
Unsaturated fats (OILS) Molecules with cis-double bonds
• trans-fats are molecules with trans double bonds • trans-fats increase the risk of cardiovascular disease
Natural Fatty Acids
linoleic acid – omega-6 fatty acid
alpha-linolenic acid – omega-3 fatty acid (9Z, 12Z, 15Z)-9, 12, 15-octadecatrienoic acid
10
10/13/2009
Asymmetric Hydrogenation of Alkenes H2 Ruthenium-based metal catalyst
P(Ph)2 P(Ph)2
(S)-BINAP
Period Table
11
10/13/2009
Asymmetric Hydrogenation of Alkenes H2 Ru-based metal catalyst
(S)-Naproxen anti-inflammatory agent
P(Ph)2 P(Ph)2
(S)-BINAP
Asymmetric Synthesis of Aspartame (S)-phenylalanine
(S)-aspartic acid
CO2H NH H2N
HO2C
H
H O
Aspartame
12
10/13/2009
Asymmetric Synthesis of Aspartame H2 Rhodium-based metal catalyst
CO2H NH H2N
HO2C
H
H O
Aspartame
13
ORGANIC CHEMISTRY 212 Lecture 13: October 13th, 2009
Youla S. TSANTRIZOS Office: Chemistry Department Pulp & Paper, Room 108 Email: [email protected]
ORGANIC CHEMISTRY 212 Chapter 7 and 8: ALKENES - the E / Z naming system - Synthesis via Elimination reactions - Hydrogenation - Addiotion of Halogenation
1
10/13/2009
Molecular Structure of Ethene (C2H4)
~ 118o ~ 121o
1
1
2s
2
3
2p
sp2
sp2
2p
+
~ 121o
Molecular Structure of Ethene (C2H4)
~ 118o ~ 121o
π H
H
H
H
σ
2
10/13/2009
Ethene (Ethylene): a Plant Hormone
Ethene (Ethylene): a Plant Hormone Photosynthesis
Glu
Glu Biosynthesis of Anthocyanins Requires the Sugar Glucose
3
10/13/2009
Reaction of Cyclopentanol with CH3CO2H H _ Br
Br -
Reaction of Cyclopentanol with CH3CO2H H _ Br
Br -
Dehydration of secondary or tertiary alcohols usually proceed via E1 elimination The stability of the carbocation is a key factor in this reaction!
4
10/13/2009
Effects of Substituents on Dehydration H
1o
OH
1o
2o
3o
H H Increasing Reactivity towards a SN1 Substitution Reaction
Increasing Reactivity towards an E1 Elimination Reaction
Dehydration Requires Acidic Conditions ! H
1o
OH
1o
2o
3o
H H
HBr
Na+ BrNO REACTION !
5
10/13/2009
Hydrogenation Reaction of Alkenes H2 metal catalyst Pd (Palladium) or Ni (Nickel) or Rh (Rhodium)
Period Table
6
10/13/2009
Hydrogenation Reaction of Alkenes
H
H
H
H
Relative Heat of Hydrogenation of Alkenes
E N T H A L P Y ∆Ho = -127 kJ/mol
∆Ho = -120 kJ/mol
∆Ho = -115 kJ/mol
CH3CH2CH2CH3 • All reactions are exothermic, the ∆Ho is the heat of reaction • All reactions require H2 and a metal catalyst • Product from all reactions is butane
7
10/13/2009
Relative Stability of Alkenes
INCREASING STABILITY
• the greater the substitution (i.e. number of attached alkyl groups) the more stable the alkene • trans-double bonds are more stable than cis, except in ring systems with less than 6 carbons
Cycloalkenes
trans-cyclohexene - evidence that it forms as a very high energy reactive intermediate NOT stable at room temperature!
8
10/13/2009
The Health Effects of trans-Double Bonds
Unsaturated fats (oils) Molecules with cis-double bonds
Essential starting materials for the Biosynthesis of hormones
Saturated fats (animal fat, butter) Molecules with NO bonds
Increase the risk of cardiovascular disease associated with high levels of cholesterol
The Health Effects of trans-Double Bonds Comparative properties of common cooking fats (per 100g) Total Fat
Saturated Fat
Monounsaturated Fat
Polyunsaturated Fat
Protein
Butter
81g
51g
21g
3g
1g
Vegetable Shortening (hydrogenated)
71g
23g
8g
37g
0g
Olive Oil
100g
14g
73g
11g
0g
Lard
100g
39g
45g
11g
0g
9
10/13/2009
The Health Effects of trans-Double Bonds The process of making margarine Vegetable oils (usually liquids) are partly hydrogenated to convert them to solid fats
Unsaturated fats (OILS) Molecules with cis-double bonds
• trans-fats are molecules with trans double bonds • trans-fats increase the risk of cardiovascular disease
Natural Fatty Acids
linoleic acid – omega-6 fatty acid
alpha-linolenic acid – omega-3 fatty acid (9Z, 12Z, 15Z)-9, 12, 15-octadecatrienoic acid
10
10/13/2009
Asymmetric Hydrogenation of Alkenes H2 Ruthenium-based metal catalyst
P(Ph)2 P(Ph)2
(S)-BINAP
Period Table
11
10/13/2009
Asymmetric Hydrogenation of Alkenes H2 Ru-based metal catalyst
(S)-Naproxen anti-inflammatory agent
P(Ph)2 P(Ph)2
(S)-BINAP
Asymmetric Synthesis of Aspartame (S)-phenylalanine
(S)-aspartic acid
CO2H NH H2N
HO2C
H
H O
Aspartame
12
10/13/2009
Asymmetric Synthesis of Aspartame H2 Rhodium-based metal catalyst
CO2H NH H2N
HO2C
H
H O
Aspartame
13
