Rules of the Day
Click here for a copy of my lecture notes from today's lecture
Click here for a copy of the handout used in class today
Watch this video that explains terpenes. This material will be on the next midterm!
Featured Golden Rules of Chemistry: 8. Reactions will occur if the products are more stable than the reactants (motive) and the energy barrier is low enough (opportunity).
1. Protons move very fast compared to other species, so fast that equilibrium in acid base reactions occurs generally before any other kinds of reactions can take place.
2.A Lewis acid is any molecule or ion that can accept a pair of electrons to make a new covalent bond, and a Lewis base is any molecule or ion that can donate a pair of electrons (lone pair or pi bond) to make a new covalent bond. (Note these definitions include proton transfer reactions in which the proton is the Lewis acid).
3. Some Lewis acids and Lewis bases will combine to form a strong covalent bond, but others form a complex with a weak type of covalent bond. The key interaction involves a lone pair from the Lewis base interacting with an electron deficient portion of the Lewis acid.4. When a Lewis acid and Lewis base combine, the product is referred to as a Lewis acid-Lewis base complex. The bond is referred to as a "coordinate covalent bond" or "dative bond".
5. Alkenes have one sigma bond and one pi bond, The reactivity of alkenes is based on the pi bond. Click here for a picture that helps you remember pi bonds.
6. The most important consequences of the pi bond are that A) the double bond cannot rotate and B) electron density is above and below the bond axis.
7. Stereoisomers of alkenes with a single substituent on each carbon atom of the double bond are named as "cis" (same side) or "trans" (opposite side).
8. Use the "E-Z" nomenclature for naming complex alkenes. Remember that "Z" means "Zame Zide". When establishing priority for for E vs. Z, it is the same as for R and S. Higher atomic number wins and count multiple bonds as being equivalent to that same number of bonds to the atoms taking part.
9. Trans alkenes are more stable than cis alkenes because cis alkanes have some non-bonded interaction strain. In addition, more highly substituted alkenes are more stable than less substituted alkenes (we don't really tell you why, just learn it.)
10. Terpenes are complex natural molecules that are built from 5 carbon "isoprene" units in Nature, especially plants. Watch the video. You are responsible for this information for the next midterm!
11. Alkenes react with H-X (X = Cl, Br, I) in a mechanism that involves initial protonation of the pi bond (add a proton) to give a carbocation intermediate, that then adds X- (make a bond between a nucleophile and electrophile) to give an haloalkane (alkyl halide). Click here to see the reaction movie of H-Br adding to propene.
12. Reactions are like crimes, they need motive and opportunity.
13. Heating up a reaction increases the rate by increasing the number of molecules with enough energy to get over an energy barrier.A. A reaction has a motive if the products are lower in energy than the starting materials. That is, stronger bonds are made than broken in the reaction, and/or a weaker acid/weaker base is produced, and/or entropy is increased through the creation of a small gaseous fragment. Motive (also called thermodynamic driving force) determines position of equilibrium.
B. A reaction has an opportunity to take place if the mechanism contains no species that are higher in energy than the energies of a resonable fraction of starting material molecules at a given temperature. Opportunity determines rate of a reaction (also called reaction kinetics).
HOMEWORK:
You must Watch the Terpene video. You are responsible for this information for the next midterm!
Read: Sections 5.1-5.4, 6.1-6.4A in the eBook.
Take the Daily Quiz 9 before 10 PM tomorrow. Click here to access the quiz. These quizzes are designed to review the important material from today's lecture. Together, they will count as 5% of your final grade.
