Chem 241

Chem 241 Review for Exam 3 / Final 12/08
McMurry 7 th Ed
Objectives: You should be able to:
1. Perform objectives for Exams 1 and 2 given on previous sheets.
Chapter 8: Alkynes: Intro to Organic Synthesis
Topics Covered:
Naming alkynes; Enyne; vicinal;
Electrophilic addition and elimination reactions; tautomers,
Lindlar catalyst, Acetylide anions
Synthesis reactions
You should be able to:
1. Name acyclic and cyclic alkynes, and draw structures corresponding to names.
2. Predict the relative stability of alkyne bonds.
3. Show reactions of preparation of alkynes:
Dehydrohalogenation of vicinal dihalides
o (2KOH, ethanol) or
o (2NaNH 2, NH 3 )
Alkylation of acetylide anions
o NaNH 2 , 2. RCH 2 X)
4. Predict the products of electrophilic or radical additions to alkenes: (remember
regiochemistry and stereochemistry)
Addition of hydrogen halides
o (1 or 2 eq HX, ether) (Markovnikov regiochemistry) or
o (1 or 2 eq HX, H 2 O 2 ) (non-Markovnikov)
Addition of water and alcohols
o (H + , H 2 O or R-OH) including carbocation rearrangements. (Markovnikov)
Addition of halogens in
o nonpolar solvent (1 or 2 eq X 2 , CH 2 Cl 2 ) (anti stereochemistry) or
o polar solvent (1 or 2 eq X 2, H 2 O) or (1 or 2 eq X 2 , R-OH) (Markovnikov + anti)
Oxymercuration
o (Hg 2 SO 4 , H 2 SO 4 , H 2 O)
Hydroboration-Oxidation
o (1. BHR 2 2. H 2 O 2 , NaOH, H 2 O)
Reduction:
o Hydrogenation (2H 2 , Pd/C or Pt/C, or Ni) (to alkane)
o Hydrogenation (H 2 , Lindlar’s cat) (to cis alkene)
o (Li or Na, NH 3 ) (to trans alkene)
5. Correctly show the mechanism of addition reactions to alkynes.
6. Perform tautomerization of enols and carbonyls and apply it to alkyne chemistry.
7. Predict and compare the stability of saturated and unsaturated carbocation intermediates.
8. Predict the relative acidities of hydrocarbons and the strength of their corresponding
bases.
9. Perform substitution reactions on alkynes using acetylide anion intermediates.
10. Synthesize a target molecule from a given starting material using reactions known to you.
11. Summarize the industrial uses of acetylene.

Chapter 9: Stereochemistry
Topics Covered:
Handedness: chiral, plane of symmetry, achiral, chiral center, plane-polarized light,
Optical activity, devorotatory, dextrorotatory, specific rotation
Stereoisomers: enantiomers, diastereomers, meso,
Configuration, absolutie configuration, racemate, resolution
Prochirality, re face, si face, prochiral center, pro-R, pro-S
You should be able to:
1. Distinguish between Constitutional isomers and Stereoisomers.
2. Recognize stereogenic centers and identify them as R or S.
3. Define and distinguish plane of symmetry, chirality, polarimeter, specific rotation.
4. Compare and contrast the physical and chemical properties of enantiomers and
diasteriomers.
5. Locate the symmetry plane of a meso compound.
6. Predict and draw the 'wedge-and-dash structures' and the Fisher projections of
stereoisomers.
7. Calculate the number of possible stereoisomers from the number of stereogenic centers.
8. Distinguish between (+), (-), dextrorotatory, and levorotatory.
9. Calculate the percent optical purity if given the enantiomeric excess.
10. Distinguish between and identify specific erythro, threo, and meso isomers.
11. Develop a plan for chemically resolving a racemic mixture.
12. Distinguish between absolute and relative configuration.
13. Distinguish between enantiotopic and diastereotopic hydrogens. Label as pro-R or pro-S.
14. Distinguish between a regioselective, stereoselective, and a stereospecific reaction.
15. Predict the stereochemistry of reaction products, using the concept of prochirality when
appropriate.