Organic structure and mechanism conventions

Structural formulae show connectivity, displayed formulae show bonds, skeletal formulae show the carbon framework, and partial-skeletal forms combine conventions. Use enough bonds and labels to make one structure unambiguous.

Show heteroatoms and their attached hydrogens, indicate multiple bonds and use the accepted benzene-ring convention. A condensed formula must still distinguish functional-group position and branching.

CH₃CH(OH)CH₃ identifies propan-2-ol; a skeletal chain with –OH at the middle carbon conveys the same connectivity.

Leaving out a carbon-bound hydrogen is normal in skeletal notation, but leaving out a heteroatom or bond needed to distinguish isomers is not.

A pair of optical isomers must have the same connectivity but opposite three-dimensional arrangement at a chiral centre. Wedge and dashed bonds show groups projecting towards and away from the page.

Keep two bonds in the plane and reverse the out-of-plane relationships to draw the mirror image. Check that the two structures cannot be superimposed by rotation.

For a carbon attached to H, OH, CH₃ and CO₂H, reflect the wedge/dash arrangement to obtain the enantiomer without changing any group identity.

A flat left/right redraw is not necessarily a mirror image, and rotating one drawing in space can make apparently different drawings identical.

An organic mechanism should show charges, bond polarity, lone pairs and curly arrows that track electron-pair movement. Curly arrows start at an electron source and end at an electron-deficient atom or bond.

Use a full step only when it changes connectivity: identify the nucleophile/electrophile, show the intermediate and restore charges and octets in the product.

In a nucleophilic substitution, draw the arrow from the lone pair on the nucleophile to the carbon and the C–leaving-group bond to the leaving group.

A curly arrow does not mean an atom moves; it represents a pair of electrons, and it must not start from a positive charge with no electron source.