Doc Brown's Advanced A Level Chemistry
Revising Advanced Level Organic Chemistry
PART 13 The Shapes of Organic Molecules and bond angles related to their Electronic Structure
Physical Organic Chemistry
or Part 3 of shapes of molecules and bond angles
A description, explanation, shapes and bond angles of a variety of organic molecules are described with dot and cross and '3D' shape diagrams to represent e.g. alkanes, halogenoalkanes, alkenes, alkynes, alcohols, carboxylic acids and derivatives, arenes, phenols etc. All is described and explained!
SHAPES OF MOLECULES INDEX: Introduction - theory - lots of inorganic molecule/ion examples * Some other molecules/ions of carbon, nitrogen, sulphur and chlorine * GCSE/IGCSE/AS Science-CHEMISTRY bonding notes
- two starter examples
These often are not given a particular shape name, but never-the-less, an appreciation of the 3D spatial arrangement is expected e.g.
Ethane consists of two joined 'tetrahedral halves', in which all C-C-H and H-C-H tetrahedral bond angles of 109o.
ball and stick model of ethane
Benzene is a completely planar molecule, with all C-C-C or C-C-H bond angles of 120o.
Shapes and bond angles of organic molecules
Most bond angles in organic chemistry can be accurately or approximately predicted using bond repulsion theory (with some notable exceptions at the end).
Some significant exceptions to the above general rules.
EXAMPLES analysed and summarised for you ...
methanol all H-C-H, C-O-H and H-C-O angles ~109o
chloromethane all H-C-H and H-C-Cl angles ~109o tetrahedral shape
propane all H-C-H, C-C-H or C-C-C angles are 109o
propene H-C-H 109o in the CH3- group, but the
propyne the H-CC and CC-C angles are 180o
methylbenzene C-C-C in ring 120o and C-C-C(H3) off the ring 120o
but the C-C-H of the C-CH3 and the H-C-H in the -CH3 off the ring are 109o
bromoethaneall H-C-H, H-C-C, C-C-Br, H-C-Br angles are 109o
ethanolall H-C-H, H-C-C, C-C-O, H-C-O, C-O-H angles are 109o
methoxymethaneall H-C-H, H-C-O, C-O-C angles are all 109o
phenolC-C-C in ring 120, C-C-H of ring 120o and C-O-H off ring is 109o
ethylamine all H-C-H, C-C-H, C-C-N and C-N-H angles are all 109o
butanone H-C-C, H-C-H and (O=)C-C-C on right are all 109o
methanoic acidH-C=O, H-C-O(-H) and O=C-O are 120o and C-O-H is 109o
ethanamide H-C-H, H-C-C, H-N-H and C-N-H are all 109o
ethyl ethanoate all H-C-H, O-C-C (right), H-C-C (left)
ethanoyl chloride H-C-H and H-C-C are 109o
diazo dye all the C-C-C, C-C-H, C-N=N, C-C-N(=) bond angles
which will eventually be replaced by neater diagrams!
SEE ALSO Appendix 1-4 on separate page: The shapes, with ox diagrams and bond angles, of some other molecules/ions of carbon, nitrogen, sulphur and chlorine besides those on this page and again the 'scribbles' will be replaced by neat diagrams eventually!
Revision notes for GCE Advanced Subsidiary Level AS Advanced Level A2 IB Revise AQA GCE Chemistry OCR GCE Chemistry Edexcel GCE Chemistry Salters Chemistry CIE Chemistry, WJEC GCE AS A2 Chemistry, CCEA/CEA GCE AS A2 Chemistry revising courses for pre-university students (equal to US grade 11 and grade 12 and AP Honours/honors level courses)
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