good nucleophilemoderate nucleophilepoor nucleophileExam #3 Study Guide Lectures: 16 - 20Lecture 16 (October 22)Know the difference between polar protic solvents and polar aprotic solvents and examples of both:- Polar aprotic solvent: solvate cations well but non anions. Therefore, anions unsolvates left as good nucleophiles.- Polar protic solvent (acidic H’s): opposite reactivity (nucleophilicity)Be able to determine a good vs. poor nucleophile:good nucleophile moderate nucleophile poor nucleophileBr -I - NH3 ROHHO - CH3 - SH H2ORS -CN -N3 -Know other rules of nucleophilicity: CHEM 333 1st Edi-tion- Within a row - moving right to left - increase in nucleophilicity as basicity increases- Anions are better nucleophiles than nueatral with regards to nucleophilic atomoExample: HO - > H2O, MeO - > HOMe, - NH2 > NH3, - S-R > H-SR- Nucleophiles with same atoms: weaker acid = stronger conjugate base = stronger nucle-ophileo Example: < HO - = RO -- Polarizable molecules are more nucleophileic- Sterics around attacking atoms reduce nucleophilicityoExample:Rules aboult alkyl halides with SN1 vs SN2:- 3o alkylhalides: only SN1 reactions- 2o alkylhalides: can do both. Depends on solvent and nucleophile.- 1o alkylhalides and methyl: only SN2 reactions- These rules apply because electronics of alkyl halides are important for SN1, whereas sterics are important for alkyl halides in SN2Rules about carbocation stability:Rules about good leaving groups:- Never a good leaving group: HO - , RO -, - NH2, H - , - CH3- Best leaving groups are weak bases after they depart- Stable anions/conjugate base of strong acids are good leaving groups:Lecture 17 (October 29) Understand SN1 and SN2, which is summarized in the following chart:SN1 SN2methyl Yes No1° alkyl halide Yes No2° alkyl halideYes- aprotic solvent- good nucleophileYes- protic solvent- poor nucleophile3° alkyl halide No Yeschiral center substitution Inversion Racemic MixtureUnderstand elimination reactions: reactions that synthesize alkenes. Also known as B (beta) elim-ination. Dehydrohalogenation takes place.- General overview:o Alkyl halide reacts wtih a strong baseExamples of strong base:- E1: unimolecular elimination reactiono rate = d [RX] = k [RX]o Products can be cis or trans in some circumstances Example:- E2: bimolecular, concerted elimnation reactions. Leaving group leaves at the same timea s the base deprotonates and double bond forms.o rate = d [RX] = k [RX][base]o E2 must have a leaving group be antiplanar for elimination to occurExample:Zaitsev’s Rule: B ellimination’s major product will be more subtituted alkene, therefore, more sta-ble alkene- Exception: will always give less substituted product. Too sterically hindered.Understand carbocation rearrangement as it applies to SN1, SN2, E1, and E2 reactions- SN1 and E1: possible rearrangement, meaning sometimes H and C can move - forms a morestable carbocation. It moves to an adjacent carbon (1,2 - shift)o Example:o Example:- SN2 and E2: no rearrangementKnow names of double bonds or cycloalkenes as substituents:- Double bond as a substituent:- Cycloalkenes: C7 or less double bond found in ring bond is cisLecture 18 (November 5)Acid catalyzed dehydration of alcohols: know reagent and how to draw mechanism and products- Example: E1 mechanism- Example: dehydration of 1° alchohol go through E2 mechanism because you can’t form a 1° carbocationAlkyne Synthesis: know reagent and how to draw mechanism and products- Example:Acetylide Substitution: know reagents and how to draw products- Example:- Reagents that can be used:, , and LDA = lithium diisopropyl amine = - Use for SN2 reactions with 1° methyl halides onlyHydrogenation of Alkenes: know reagents and how to draw products- Example:- Example:Alkyne Reduction: know reagents and how to draw products- Examples of syn addition of H2 -Z alkenes:- Example of anti addition of H2 -E alkenes:Know how to work an organic synthesis problem: process of building organic molecules. Can be one step or many steps. Put togeter a strong of reactions - multi-step synthesis. Do not give mechanisms in synthesis problems, just give reagents and products. Use retrosynthetic analysis - working backwards from target molecule.- Example:Lecture 19 (November 7) Addition of HX: know reagents and how to draw products. It is regioselective, so you get one product out of the two products possible.- Example: Cl goes to the more substituted carbon (Markovnikov product)- Example:- Mechanism:- Markovnikov Rule: get more stable carbocation, therefore, X goes to more substituted car-bonoExample:- Example: If carbocation forms, rearrangement can occurAcid Catalyzed Hydration: acid is usually H2SO4. H2O adds to alkene to get alcohol. Know reagents and how to draw products.- Example: OH goes to more substituted C. Markovnikov addition of OH.- Mechanism:Addition of Cl2 or Br2: know reagents and how to draw products.- Example:- Example:Lecture 20 (November 12)Br2 or Cl2 addition in the presence of H2O or R-OH: know reagents, mechanism, and how to draw products.- Example:oMechanism:- Regioselective reaction: X- adds to less substituted side of doube bond. OH adds to more substituted side of double bond. X and OH are anti to each other.oExample:- Can substitute H2O with an alcohol (R-OH)oExample:- Can have internal attack of an alcohol onto a brominium/chlorinium ion to make a 5 or 6 membered ringoExample:Oxymercuration-Reduction: know reagents and how to draw products.- Example:- Example:- Example: goes through carbocation. Look for rearrangements.- Example: no carbocation, so no rearrangementHydroboration/Oxidation: anti-Markovnikov addition of OH across a double bond. Know reagentsand how to draw products.- Example:- Example:- Example:Oxidation: OsO4 is used as reagent. Know how to draw products.- Example:Ozonolysis: cleavage of a cdouble bond to 2 carbonyls. Know how to draw products.- Example:-