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I. Introduction into Redox Reactions
Rx of Sugars I. Introduction into Redox Reactions
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Redox Reactions All reactions exchange electrons
The substrate that gains e- is reduced The substrate that loses e- is oxidized Indicated by brackets
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Another helpful acronym
"OIL RIG" O Oxidation I Is L Loss of electrons R Reduction G Gain of electrons
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Oxidation Numbers Oxidation numbers, ON, are a measure how oxidized (or reduced) an element is The more negative the ON, the more reduced an element is Comparing ON before and after a Rx shows if an element was oxidized or reduced Ex: → symbolizes Oxidation O → symbolizes Reduction
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Example
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Assigning Oxidation numbers
1. Ions/Ionic compds: ionic charge = ON O2- : -2 CaO : Ca2+ O2- so Ca: +2 O: -2 Pb(SO4)2 Pb: ____ SO4: ____ 2. Diatomic molecular compounds: neutral H2, O2 : 0 3. Monoatomic Metals: neutral Mg: 0
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4. ON in Molecular compounds
Finding ON from elements in molecules Add up ON from ligands: a) Oxygen: (High EN 3.5) is always -2 b) Hydrogen: ( low EN is 2.1) is always +1 Carbon: will assume ON so overall neutral CH4: H: +4 H3COH H: +4 C: -4 O: C: -2 0
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Oxidation number of elements in molecules
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Problem: e- are invisible! Use transfer of O and H
Reduction: gain of H or loss of O Oxidation: gain of O or loss of H Example: Carbon: oxidized lost H Oxygen: reduced gained H
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Example
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Reducing and Oxidizing Agents
XH + Y → X + YH Reducing Agent is a substance (X) that reduces another substance and becomes oxidized in the process Oxidizing Agent is a substance that…..opposite
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Oxidation of Monosaccharides Testing for reducting sugars: Benedict’s Test
Glucose is __________ and is a(n)________agent Copper is ___________ and is a(n) ________agent Cu2+ copper is (___) →Cu2O copper (___) Cu+SO3 + Cu2O red +Cu2+ blue +O2
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Oxidation of Disaccharides
All disaccharides that have an accessible α/β in the 2nd monosacch. can open and oxidize Which of our 3 disaccharides can oxidize?
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Oxidation of Polysaccharides
do not oxidize are not reducing carbs
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