1 I. Introduction into Redox ReactionsRx of Sugars I. Introduction into Redox Reactions

2 Redox Reactions All reactions exchange electronsThe substrate that gains e- is reduced The substrate that loses e- is oxidized Indicated by brackets

3 Another helpful acronym"OIL RIG" O Oxidation I Is L Loss of electrons R Reduction G Gain of electrons

4 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

5 Example

6 Assigning Oxidation numbers1. 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

7 4. ON in Molecular compoundsFinding 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

8 Oxidation number of elements in molecules

9 Problem: e- are invisible! Use transfer of O and HReduction: gain of H or loss of O Oxidation: gain of O or loss of H Example: Carbon: oxidized lost H Oxygen: reduced gained H

10 Example

11 Reducing and Oxidizing AgentsXH + 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

12 Oxidation of Monosaccharides Testing for reducting sugars: Benedict’s TestGlucose 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

13 Oxidation of DisaccharidesAll disaccharides that have an accessible α/β in the 2nd monosacch. can open and oxidize Which of our 3 disaccharides can oxidize?

14 Oxidation of Polysaccharidesdo not oxidize are not reducing carbs