I. Introduction into Redox Reactions Rx of Sugars I. Introduction into Redox Reactions

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

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

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: +4 → + 2 symbolizes Oxidation O → -2 symbolizes Reduction

Example 0 +2 +2 0

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

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: -2 0 +2 C: -2 0

Oxidation number of elements in molecules

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

Example  

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

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

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?

Oxidation of Polysaccharides do not oxidize are not reducing carbs