CHEM 110 Lecture Notes - Lecture 25: Pi Bond, Acetylene, Benzene
Friday, November 3, 2017
Functional Groups
CHEM 110
-Hydrocarbons
•Must be only hydrogens and carbons
•Double or triple bonds —> additional functionality (hence “functional groups”)
•Extremely flammable (often used for fuel)
•Alkanes: Saturated, sigma bonds, tetrahedral, sp3
-Example: Gas on stove (methane)
•Alkenes: Unsaturated, sigma and pi bonds, trigonal, sp2
-Example: Ethylene (bananas)
•Alkynes: Unsaturated, sigma and 2pi bonds, linear, sp
-Example: Ethyne
-Hydrocarbon Rings
•Cycloalkanes and cycloalkenes
-“alkanes” = single bonds
-“alkenes” = double bonds
-Not so common
•Aromatics (benzene rings):
-Special kind of hydrocarbon ring
-Unsaturation = Hydrogen deficiency
•Comparing # of hydrogens to carbons in a molecule
•As soon as you make a pi bond or ring, you take out hydrogens
•2 hydrogens as 1 unit of unsaturation
-For loss of every 2 Hs = 1 unseat unit
•We will never deal with odd number of hydrogens
-Boiling/Melting Point Trends
•Hydrocarbons are non polar molecules
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CHEM 110 Full Course Notes
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Document Summary
Hydrocarbons: must be only hydrogens and carbons, double or triple bonds > additional functionality (hence functional groups , extremely ammable (often used for fuel, alkanes: saturated, sigma bonds, tetrahedral, sp3. Example: gas on stove (methane: alkenes: unsaturated, sigma and pi bonds, trigonal, sp2. Example: ethylene (bananas: alkynes: unsaturated, sigma and 2pi bonds, linear, sp. Not so common: aromatics (benzene rings): Unsaturation = hydrogen de ciency: comparing # of hydrogens to carbons in a molecule, as soon as you make a pi bond or ring, you take out hydrogens, 2 hydrogens as 1 unit of unsaturation. For loss of every 2 hs = 1 unseat unit: we will never deal with odd number of hydrogens. Boiling/melting point trends: hydrocarbons are non polar molecules. Saturated functional groups: halides (primary secondary or y, tertiary bonds, r is a general symbol to represent any alkyl group (rest of the molecule) Alkyl halides (r-x): x being a halogen such as cl or f.
