The following three slides leads students to realize that free rotation around C=C bonds does not occur at room temperature.

Characteristics of  and  Bonds  bonds  bonds  bonds formed from end to end  bonds formed from side interaction to side interaction ______ orbital overlap a.more, lessb. less, morec. same______ bond______ reactive

 bonds  bonds  bonds formed from end to end  bonds formed from side interaction to side interaction ______ orbital overlap a.more, lessb. less, morec. same stronger__ bond 80 – 90 kcal/mole weaker_ bond 66 kcal/mole less__ reactivemore__ reactive

Characteristics of  and  Bonds cylindrically symmetricalnot cylindrically symmetrical ~ > 3-5 kcal/mole p orbitals must be in same required for rotationplane for  bond. What happens to the bond if the orbitals don't overlap? a. Nothingb. bond becomes strongerc. bond breaks “Free" rotationHow much energy is required occurs at room temp.for rotation? Will free rotation occur at room temperature? a. nob. yesc. can’t predict

Alkynes Which has the greatest overall bond strength in the 3 structures? a. C-C bond of ethaneb. C=C of ethylene c. C  C of acetylene d. no difference

Which compound will form preferentially? A or B

Acid-Base Reactions When an alkene reacts wit H-X, this is also a Lewis Acid-Base reaction. Which is the Lewis acid and which is the Lewis base? a.alkene = Lewis acid, H-X Lewis base b.alkene = Lewis base, H-X = Lewis acid

The next two slides explains the exothermicity of additions across  bonds.

Overall Reaction: Favorable or Not In this reaction, 1  bond and 1  bond is being replaced with 2  bonds.

Overall Reaction: Favorable or Not What would you expect to be stronger 1  bond and 1  bond or 2  bonds? Would you expect the reaction to be favorable or unfavorable then? a.1  bond and 1  bond and the reaction would be favorable b.1  bond and 1  bond and the reaction would be unfavorable c.2  bonds and the reaction would be favorable d.2  bonds and the reaction would be unfavorable

Forward Reaction : elimination of H-Br from bromoalkane to give alkene Reverse Reaction : What is happening in the reverse reaction? a. S N 2 reaction b. S N 1 reaction c. E1 reaction d. E2 reaction e. Addition reaction

Electron density is easily donated. Why? a.  bond weaker than  bond b.  electrons more accessible c. Both a and b d. Electrons on atom with high electronegativity

Which of the following could initiate the cationic polymerization of styrene?

Enter the #’s of the reagents in the proper sequence that will synthesize 1- methylcylcohexanol from 1-methylcyclohexene

Enter the #’s of the reagents in the proper sequence that will synthesize 1-methylcylcohexanol from (bromomethyl)cyclohexane

The next 3 slides compares the mechanism in a biological hydration to the recently covered acid catalyzed hydration.

Citric Acid Cycle aconitase : enzyme (m.w.  89000)

Hydration of cis-Aconitate to Isocitrate

Hydration of cis-Aconitate to Isocitrate After 180  Flip Is this the same mechanism as that shown for the addition of water to 2- methypropene using sulfuric acid as a catalyst? a. Yesb. No c. Can’t be distinguished

The next 2 slides are part of one question.

An Example of a Biological Electrophilic Addition Biosynthesis of  -Terpineol (found in pine oil)

Which of the following in not a step in the mechanism of the reaction?

Hydroboration Which way would the B-H bond prefer to add if steric hindrance wasn’t a factor?

Which structures appears to have less electron repulsion between the atoms?

What would be the structure of the polymer formed from cationic polymerization of 2- methylpropene? a.b. c. d.d. e.

Which of the following is a step in the mechanism for the following reaction if it is acid catalyzed? a.b.c. d.e.

Which of the following is a major product of the following reaction used in carbohydrate synthesis? a.b.c. d.e.

Predict the major stable product of the following reaction.

The next 5 slides asks students to explain experimental results after they have already learned something about electrophilic addition.

Bottle contains bromine in water Left test tube contains cyclohexane Right test tube contains cyclohexene

Bromine/H 2 O is added to each test tube

After Shaking

A Chemical Reaction Occurred Which compound reacted? a.Cyclohexaneb. Cyclohexene What type of bond most likely was involved in the reaction? a. C-H  bondb. C-C  bondc.  bond

What might be a product of the reaction? (H 2 O is a complicating factor covered later)

Mechanism of X 2 Addition to Alkenes In the first step, what is the reactive intermediate formed called? a. cyclic halide ion b. cyclic halidium ion c. cyclic carbocation d. cyclic halonium ion e. cyclic halocarbocation

Mechanism of X 2 Addition to Alkenes What reaction does the second step look like? a. E2 b. Addition of HX c. S N 2 d. S N 1 e.E1 (reaction of bromide anion with cyclic halonium ion)

Mechanism of X 2 Addition to Alkenes Why does only the trans product form? a. The reactive intermediate is resonance stabilized. b. The reactive intermediate is stabilized by the alkyl groups. c. S N 2 reactions require backside displacement. d. The trans product is more stable. e. The bromide ion is too unreactive.

Predict the major product of the following reaction.

Catalytic Hydrogenation of Alkenes Does this appear to be a syn or anti addition? a. synb. antic. neither

Carbenes Based on this structure, would you expect a carbene to be an electrophile or nucleophile? a. nucleophileb. electrophilec. neitherd. both

Oxidation of Alkenes to Diols How could the trans diol be synthesized from cyclohexene?

Predict the major stable product(s) of the following reaction.

How could the oxirane be synthesized from but-2-yne?

In the biosynthesis of fatty acids, the crotonyl ACP is converted to butyryl ACP. What type of reaction does it formally appear to be? a. dehydrationb. hydration c. alkyl shiftd. hydrogenation e. hydride shift