Review Of Organic Chemistry

ADVERTISEMENT

Organic Chemistry I Review: Highlights of Key Reactions, Mechanisms, and Principles
1
Some Arrow-Pushing Guidelines (Section 1.14)
1. Arrows follow electron movement.
2. Some rules for the appearance of arrows
• The arrow must begin from the electron source. There are two sources:
a. An atom (which must have a lone pair to give)
b. A bond pair (an old bond that breaks)
• An arrow must always point directly to an atom, because when electrons move, they
always go to some new atom.
3. Ignore any Spectator Atoms. Any metal atom is always a “spectator”
• When you have a metal spectator atom, realize that the non-metal next to it must have
negative charge
4. Draw all H’s on any Atom Whose Bonding Changes
5. Draw all lone-pairs on any Atom whose bonding changes
6. KEY ON BOND CHANGES.
Any two-electron bond that changes (either made or
broken) must have an arrow to illustrate:
• where it came from (new bond made) or
• an arrow showing where it goes to (old bond broken)
7. Watch for Formal Charges and Changes in Formal Charge
• If an atom’s charge gets more positive Þ it’s donating/losing an electron pair Þ arrow
must emanate from that atom or one of it’s associated bonds.
There are two “more
positive” transactions:
• When an anion becomes neutral. In this case, an arrow will emanate from the
atom. The atom has donated a lone pair which becomes a bond pair.
• When a neutral atom becomes cationic. In this case, the atom will be losing a
bond pair, so the arrow should emanate from the bond rather than from the atom.
• If an atom’s charge gets more negative Þ it’s accepting an electron pair Þ an arrow must
point to that atom. Ordinarily the arrow will have started from a bond and will point to
the atom.
8. When bonds change, but Formal Charge Doesn’t Change, A “Substitution” is Involved
• Often an atom gives up an old bond and replaces it with a new bond.
This is
“substitution”.
• In this case, there will be an incoming arrow pointing directly at the atom (to illustrate
formation of the new bond), and an outgoing arrow emanating from the old bond that
breaks

ADVERTISEMENT

00 votes

Related Articles

Related forms

Related Categories

Parent category: Education