• The pieces at right are the different “elements”
you can use to build the molecule. Obviously, not
all will be used in any given molecule, and some
will be used many times over.
• To build a new element, fill in the bubble next to
the corresponding letter, as well as a bubble for
the previously built element to which it is connected. The number to the left of the rows of bubbles is the
number used to refer to this element when connecting later elements.
• Although the atoms are generally portrayed above as sp3, if connected by a double or triple bond (see below),
they may instead be sp2 or sp hybridized.
• Start with carbon atom of the principal FG, or the end of the chain closest to the principal FG. Place only the
carbon atom (with attached H’s) initially – any other heteroatoms (non-C/H atoms), including those making up
the principal FG, will be added later.
• Continue adding only carbons (with the appropriate number of H’s) to the end of the principal chain.
o Do not add any non-H atoms (-OH, =O, etc.) until the principal carbon chain is complete.
o As you continue to add only C’s and H’s, there will be vacant valences (visualized above with dotted
lines) where non-H FG atoms or other substituents will be added later. For example, you would fill the
bubble for the CH of an aldehyde, then continue down the principal chain with C/H’s. The =O to
complete the aldehyde will be added later, after the principal chain is complete.
o In order to create a ring, when adding a new element, fill in the bubble next to two numbers in order
to show that the new element being added is bonded to two existing elements.
• Starting again at the principal FG (or the end of the principal chain closest to it), place any non-H FG atoms or
substituents on each carbon. Complete each FG or substituent before moving on to the next.
o For aldehyde, nitrile, amide, ester or acid – complete this principal FG with all necessary heteroatoms
before moving on to other substituents, placing the carbonyl first (for amide, ester, and acid).
o For acid or amide, add any H’s on the principal FG before moving on to other substituents. (For an
aldehyde, the H should have been added with the initial “CH” placement, since it is attached to the
carbon atom on that end of the principal chain.)
o For esters, add the “-O-R” substituent and complete it before moving down the principal chain to other
substituents.
o Similarly for amides, place any “-N-R” substituents (if any) after any N-H atoms, but before moving
on to other substituents.
o For aromatic derivatives, the benzene ring completes the principal chain. For a benzoate ester, C
would be placed first, then Ph (on the C), then =O (on the C), then -O- (on the C), then the alkyl group
on the -O-, and then finally other substituents around the ring (using o/m/p).
• When adding an element connected by a double- or triple-bond, fill the corresponding bubble – any element
added with neither of those circles filled is connected by a single bond. For example, to make a carbon into a
carbonyl, you would fill in the bubble for “O”, then the number corresponding to the previously existing
carbon atom it is attached to, and then the bubble for “double”. To make a nitrile, you would select the bubble
for “N”, then a number for the C atom, and finally “triple”.
• When adding a second connection to a benzene ring (as well as any subsequent connections), use the “ortho”
“meta” and “para” labels to indicate relative regiochemistry. Those labels are always relative to the first
connection on the ring.
• You do not need to add H’s to every unsubstituted carbon on an aromatic ring – any carbon where a
substituent is not added to a benzene ring is assumed to have one -H.
• You should generally only need to explicitly add -H atoms to oxygen or nitrogen atoms.
• For now, I have not made any attempt to specify stereochemistry of any connections (cis/trans, E/Z, R/S).
Maybe sometime, but not now.
