Reactions of Organic Functional Groups Part 1: Acid-Base
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Reactions of Organic Functional Groups Part 1: Intro & Acid-Base Review Each functional group has unique chemical reactivity. Biological molecules can become very large – remember to focus on the functional groups. Most reactions only affect one functional group of a reactant at a time. Recognize the functional groups and look for changes to understand chemical reactivity. Circle the functional group that changes in the reaction below. O O OH OH O OH Almost ALL biochemical reactions are catalyzed by enzymes. What are catalysts? Why do our bodies need enzymes? Draw the Reaction Energy Diagram for a 1-step, exothermic rxn with a large activation energy. Overlay another curve showing the rxn with a catalyst.
Transcript of Reactions of Organic Functional Groups Part 1: Acid-Base
Reactions of Organic Functional Groups Part 1: Intro & Acid-Base Review
Each functional group has unique chemical reactivity. Biological molecules can become very large – remember to focus on the functional groups. Most reactions only affect one functional group of a reactant at a time. Recognize the functional groups and look for changes to understand chemical reactivity.
Circle the functional group that changes in the reaction below.
O
O
OH
OH
O
OH Almost ALL biochemical reactions are catalyzed by enzymes. What are catalysts? Why do our bodies need enzymes? Draw the Reaction Energy Diagram for a 1-step, exothermic rxn with
a large activation energy. Overlay another curve showing the rxn with a catalyst.
Acid-Base reactions are the most fundamental & frequent biochemical rxn. Complete the acid-base reactions below.
O
O
OH + NaOH 1)
OH
OH
N
HOH
+ HCl 2) Solubility and Acid-Base Chemistry
Classify each functional group and predict water solubility for the reactants and products below.
O
OH
O
O-Na
+ + OH2
NaOH
2
N
OH H
ClH NH
OH H + Cl
-
Acid Base Reactions have very low activation energies. Other Biochemical Reactions have larger activation energies. Metabolism: We will study 4 of the biochemical reactions that require catalysts:
1) oxidation-reduction 2) hydration-dehydration
3) acyl group transfer 4) phosphoryl group transfer
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Reactions of Organic Functional Groups Part 2: Redox Introduction (Oxidation & Reduction)
Oxidation & Reduction Reactions of Inorganic Molecules Guidelines for Assigning Oxidation Numbers
Oxidation numbers are a way to keep track of electron flow in reactions. The oxidation number is the charge an atom in a compound would have if the electron pairs in each covalent bond “belonged” to the more electronegative atom.
Oxidation Number Examples Exceptions
Pure elements
0 The oxidation numbers for each atom in Fe(s) or O2 is zero.
none
Fixed charge
metals
The oxidation number is equal to
its charge.
Alkali metals +1 Alkaline earth metals +2 Aluminum +3
none
F in compounds
-1
F in CaF2 is -1. F in CF4 is -1.
none
Cl, Br, & I in compounds
-1 if bonded to a less electronegative
atom
Cl is +1 when bonded with F. Cl is -1 when bonded with Br.
none
O in compounds
-2
O in MgO is -2. O in H2O is -2.
O is -1 in peroxides.
H in
compounds
+1
H in H2O is +1.
H is -1 when combined with metals.
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Practice recognizing Redox Rxns Balance the following reaction & assign oxidation numbers to each atom.
Fe2O3 + CO Fe + CO2 a) Which element is oxidized? b) Which element is reduced?
Assign oxidation numbers to each atom in the following reaction. CuO(s) + H2(g) Cu(s) + H2O(g) Writing the Oxidation ½ rxn Writing the Reduction ½ rxn
Oxidation & Reduction of Organic Molecules
Oxidation: Gain bonds to Oxygen Lose bonds to Hydrogen Reduction: Lose bonds to Oxygen Gain bonds to Hydrogen
Example – Breathylzer Test (Organic and Inorganic Redox Combined)
OH+ H2Cr2O7 OH
O
+ Cr2O3
Treatment of CH3CH2CH2CH2CHO with a reducing agent will produce A) an aldehyde. B) a carboxylic acid. C) an alcohol. D) an alkene. E) a ketone.
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Classify the following reactions as oxidation or reduction.
OH
OH
O
O
For the reactions below, a) Predict the products for the reactions below. Remember: benzene rings are very stable so they will not react. b) Classify each function group. For alcohols, remember to indicate 1, 2, or 3.
H
O
[H] [O]
[O]OH
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Oxidizing Agents: reactant that gets reduced Reducing Agents: reactant that gets oxidized For the following reaction
Zn(s) + 2 HCl(aq) Zn2+(aq) + H2(g) + 2 Cl-(aq)
a) Write the oxidation half reaction. b) Write the reduction half reaction.
c) Which reactant is the oxidizing agent? d) Which reactant is the reducing agent?
Reactions of Organic Functional Groups Part 3: Redox of ROH & Carbonyls
Oxidation of Alcohols
Ethanol Metabolism – The oxidation of a 1 alcohol
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Reduction of Carbonyl Groups
Use your knowledge of oxidation reactions to complete the reduction pathways in the following diagram. Classify the functional groups (aldehydes, ketones or alcohols) – for the alcohols indicate whether they are 1, 2, 3.
In biochemical reactions, reduction of carbonyl groups is carried out by NAD+ or NADH?
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Antioxidants Not ALL Oxidation is Beneficial. Oxidation reactions form Free Radicals. Antioxidants are substances that trap the odd valence electron to prevent it from causing damage to our biomolecules. Oxidation from Free Radicals is linked with biological aging. Many antioxidants trap the unpaired electron in an aromatic benzene ring. Vitamin E is an antioxidant. Vitamin E
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Reactions of Organic Functional Groups Part 4: Hydration-Dehydration Hydration-Dehydration Reactions Hydration of Alkenes Produces Alcohols Dehydration of Alcohols Produces Alkenes Practice reactions.
+ H2O
- H2O
a)
+ H2O
- H2O
b)
c) step 2 in the break down of fatty acids
O
SCoA
H2O
Reactions of Organic Functional Groups Part 5: Acyl Transfer What is an “Acyl Group”? Acyl Group Transfer Reactions – 2 Pathways Catabolic & Anabolic Acyl Group Hydrolysis Reactions
What happens to carboxylic acids at physiological pH? Draw the structure of acetic acid at physiological pH. The ester for apple flavoring is methyl butanoate. Draw the skeletal-line structure for apple flavoring. Write the hydrolysis reaction for apple flavoring at physiological pH.
What happens to amines at physiological pH? Draw ethanamine at physiological pH. Predict the products of the following enzyme catalyzed hydrolysis reactions at physiological pH.
NH
OH2O
enzyme
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Acyl Derivative Formation
Add the missing reactants. Show the reaction to form rum flavoring (ethyl formate) using acyl derivative formation.
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Predict the hydrolysis products of aspartame at physiological pH.
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Reactions of Organic Functional Groups Part 6: Phosphoryl Grp Transfer What is the effect of physiological pH on phosphate esters?
P
O
OHRO
OH
pH 7.4
Phosphoryl Group Transfer Reactions
Phosphate esters are formed when 1 or more of the H atoms of phosphoric acid is (are) replaced with 1 or more R groups.
Phosphoanhydride bonds form when the O atoms of one phosphate group
bonds with the P atom of another phosphate group.
Label the Phosphate groups (Pi), Phosphate ester bonds and Phosphoanhydride bonds in the compound below.
Phosphoryl groups play an important role in glycolysis. Glycolysis is the biochemical pathway that breaks down glucose to produce energy. 1st step of Glycolysis
Phosphoryl groups also play a central role in the way energy is transferred in biochemical reactions. Our body stores and transports energy in the phosphoanhydride bonds of ATP. Draw an arrow to the phosphoanhydride bond that is broken and reformed as ATP converts back and forth to ADP.
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Reactions of Organic Functional Groups Part 7: Coenzymes & Redox Rxns Oxidation and Reduction reactions ALWAYS occur together. To oxidize or reduce a biological molecule, we need a second compound that can donate or accept the electrons. Coenzymes are the second compound. Coenzymes: special molecules that shuttle electrons Common Oxidizing and Reducing Agents
Oxidizing Agents Formula or Rxn Bleach NaOCl Oxygen O2 Hydrogen peroxide H2O2 Chromium(VI) Cr6+ Manganese (VIII) MnO4- NAD+ Coenzyme
NAD++ 2H+ + 2e- NADH + H+ FAD Coenzyme
FAD + 2[H] FADH2 Reducing Agents
Hydrogen H2 NADPH Coenzyme
NADPH + H+ NADP+ + 2[H] Note the difference
Coenzymes – a closer look at the 3 Most Important FAD/FADH2 FAD is the H Acceptor when C=C (double) bonds form
Circle the reactive region of FAD and FADH2.
Diagram the reaction below to indicate the oxidation and reduction ½ reactions. Label each ½ reaction (oxidation or reduction). For the coenzyme, label FAD/FADH2.
2
O
OHO
OH
+
O
OHO
OH
+
NAD+/NADH NAD+ is the H Acceptor in Most Oxidations Diagram the reaction below to indicate the oxidation and reduction ½ reactions. Label each ½ reaction (oxidation or reduction). For the coenzyme, label NAD+/NADH.
H
O
+ OH +
NADPH/NADP+ NADPH is the H Donor in Reduction Reactions
Diagram the reaction below to indicate the oxidation and reduction ½ reactions. Label each ½ reaction (oxidation or reduction). For the coenzyme, label NADPH/NADP+.
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The reactions for two important pairs of coenzymes are shown below. a) Name them: NAD+, NADH, FAD, and FADH2. Hint: Look closely at the chemical structures to find the differences. b) Label each one of the coenzymes as an oxidizing agent or reducing agent. Reaction 1
N
N
N
N
NH2
OH OH
OP
O-
O
O
PO
O-
O
O
OHOH
N+
NH2
OH
N
N
N
N
NH2
OH OH
OP
O-
O
O
PO
O-
O
O
OHOH
N
NH2
OH H
a) b)
N
N
N
N
NH
N
O
O
O
PO
OH O
PO
OO
OH OH
N N
NH2OH
OH OH
OH
N
N
NH
N
NH
NH
O
O
O
PO
OH O
PO
OO
OH OH
N N
NH2OH
OH OH
OH
Reaction 2 a) b)
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