CHEM1200 Summary Notes PDF

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Download CHEM1200 Summary Notes PDF

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CHEM1200 Summary Notes Module 1 Lecture 1 READINGS: Sections 16.1 and 16.2 from textbook. Assessments: - Lab practical assessments (25%) - Sapling online quizzes (10%) - Mid-semester exam (20% - Final exam (45%)

Isomers and Stereoisomers Stereochemistry: - Actual shapes of molecules - The spatial arrangements of atoms within molecules - The different spatial arrangements have consequences for how they react and what properties they obtain Conformational isomers: - Has single bonds that are ‘rotatable’ due to “end-on” overlap of sp3 orbitals - E.g. ethane CH3-CH3 o Can twist one CH3 with respect to the other - Staggered conformation of ethane (CH3CH3) o Staggered conformation (“zig-zag”)  Most stable (lowest energy)  C-H bonds experience maximum separation  Remember: Each C is sp3 hybridised and bond angles are actually 109.5 degrees not 120.

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Eclipsed conformation of ethane (CH3CH3) o Eclipsed conformation (highest energy) o Least stable because of repulsion between bonding electrons o C-H bond are aligned – repulsion between bonding electrons o If you look from one side of the molecule, the molecules from one side will eclipse the other side

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Two major conformations of ethane (CH3CH3) -

Conformational energy for ethane

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At room temperature, rotation is easy and rapid (“free rotation” - molecule is free to rotate) As these bonds rotate it involves a mixture of all possible conformations but...