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CHEM 281 (42)
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Department
Chemistry
Course
CHEM 281
Professor
John Carran
Semester
Fall

Description
How to Interpret and Write Structural Formulas USE THIS ONE Dash Structural Formulas → atoms joined by single bonds can rotate relatively freely with respect to one another **if chemical structure drawn with just lines (no wedges or dotted lines) can't say anything about steric chemistry Condensed Structural Formulas Bond-Line Formulas → sp hybridization at centres: tetrahedral: angle 109 usually forcing to have angles of 60o Three-Dimensional Formulas C 2 5 Chiralcent3:CH CH 3 3 ← examples of bond-line formulas that include three-dimensional representations 1 - chiral centres circled 2 - diastereoisomer: each have different properties → to get enantiomer switch wedge and dashes of H and OH - enantiomers don't have different properties, besides how diffuse light sp hybridized carbon example w/ trigonal planar geometry sp example w/ linear geometry → sp hybridized carbons sp3 Alkyne: H Periodic Table of Elements - everything alkenes do but better (twice as • e.g. carbon is in group IVA much) ◦ carbon has 4 valence electrons -b/c of two pi bonds vs one in alkenes • e.g. nitrogen is in group VA ◦ nitrogen has 5 valence electrons - this particular alkyne: terminal alkyne - terminal alkyne = acidic ◦ 2 used as lone pair, tends to form 3 bonds • e.g. halogens are in group VIIA (hydrogen at end) - ◦ F, Cl, Br, I all have 7 valence electrons - end up with alkynil ion =C The Strucutral Theory of Organic Chemistry • # of covalent bonds usually formed by some elements typically encountered in organic compounds P:# bonds = 3 or 5 • Thus ◦ C is tetravalent ◦ O is divalent ◦ H and halogens are monovalent Carbon IMPORTANT **Important: do not draw any structure with more than 4 bonds on a carbon - ** 3 bonds on carbon → need a charge on carbon movement of one e Empty p orbital breakingbond missing→ Br 3 sp - movement of 2 e sp 2
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