CHM136H1 Lecture 8: Alkanes & their stereochemistry
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24 Jan 2019
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Alkanes & Their Stereochemistry (Lecture 8)
Alkane Nomenclature (EXPECTATION → when given a name, draw the molecule)
1. Find the longest (parent) hydrocarbon chain
2. Number carbons in this chain in sequence, starting at end nearest branch point
3. Number substituents
4. Write compound name as a single word: hyphens between prefixes, commas between
numbers
Eg. Draw 4-methyl-3-(1-methylethyl)octane ⇒ NOTICE how the 1-methylethyl group is an
isopropyl
Chemical Properties of Alkanes
- Called “paraffins” (ie. low affinity compounds) because they are fairly unreactive
- Will burn in a flame (ie. react with O2) to form CO2, H2O, and HEAT
- Not soluble in water (because of non-polar C-C & C-H bonds)
- Boiling point & melting point increases as alkane size increases (more dispersion forces)
Alkane Conformations
- Conformations → different arrangement of atoms resulting from bond rotation (one
specific conformation is a conformer)
- HOWEVER, perfect free rotation is NOT observed (since one conformation may
be more stable than others)