O2 O3 X2 H2O2 NaOCl CrO3 or any Cr2 PCC KMnO4 OsO4 Ag2O HClO4 HIO4 Reducing Agents H2 Li Na K NaBH4 LiAlH4 Reduction of alkynes to trans alkenes Na and liq. NH3 (sometimes with EtOH) Two Hs added to opposite sides of alkene Reduction of Alkynes to Cis alkenes H2 and Lindlar's catalyst (Pd, quinoline, CaCO3, Pb(OAC)2) Two Hs added to same side of alkene Alkynes are more reactive than alkenes and Lindlar’s is too weak for alkenes Reduction of alkenes to alkanes (Catalytic Hydrogenation) H2 excess, catalyst (Ni, Pd, Pt, Pd/C) Exothermic Always syn addition of Hs Reduction of alkynes to alkanes (Catalytic Hydrogenation) H2 excess, catalyst (Ni, Pd, Pt) 4 Hs added Stability of Alkenes More substituted is more stable Trans is more stable than cis Reduction of alkyl halides to alkanes w/LAH Also written LiAlH4 SN2 rxn X is substituted with H X = I > Br > Cl (not F) Rate of rxn : Me > 1 > 2 (not 3) Epoxidation of alkenes w/ Peracids Alkene forms epoxide Rxn is stereospecific (if it starts cis the epoxide ends in cis) Weakest O-H bond from peroxide moves 1 step rxn no intermediate Common peracids: MCPBA and MMPP Oxidative Cleavage of Alkenes O3 H2O, CH3SCH3, PPh3 Cut in half at alkene and add =O to make aldehyde or ketones Oxidative cleavage of Alkynes (Ozonolysis) O3 H2O, CH3SCH3, PPh3 Internal Alkyne: cut in half and make two carboxylic acids Terminal Alkyne: cut in half and make carboxylic acid and CO2 PCC Oxidation (Pyridinium chlorochromate) Soluble in organic solvent Stops at aldehyde and doesn't go to COOH even with primary OH O becomes double bonded and H attaches to C Oxidation of Alcohols Primary [O] aldehyde [O] carboxylic acid Secondary [O] ketone Tertiary [O] no rxn [O] conditions: Na2Cr2O7 or K2Cr2O7 over H2SO4, H2O And H2CrO4 over acetone (jones reagent) Anti - 1,2 - dihydroxylation Peracid H+ or OH- in H2O OH added to opposite sides of C-C bond First peracid makes an epoxide where R1 and R3 stay cis so dashed Then second step opens ring with OH on straight bonds If cyclo then racemic mixture of OH on dashed and wedged Syn - 1,2 - dihydroxylation 3 conditions: Cold KMnO4 over OH- and H2O Cat OsO4, NMO 2) NaHSO3, H2O OsO4 2) NaHSO3, H2O OH added to straight bonds on same side of C-C bond Needs to be rotated 180 for final product where OH is across from each other Chapter 13 Breaking into radicals : homolytic cleavage and endothermic Radicals are sp3, trigonal planar, 120, empty p-orbital Most stable to least stable: 3 > 2 > 1 > methyl Why? Hyperconjugation (R groups stabilize radical C) Induction (electrons flow from sp3 C to sp2 C) How do radicals react Radicals attack sigma bonds: radical hits bond and takes H Radicals attack pi bonds: radical hits bond and attaches to C Radicals attack radicals: coupling exothermic Alkanes w/ Halogens Exothermic R-H + X2 with light and heat makes R-X + HX X2 is either Cl or Br Alkane w/ Cl2 Initiation: Cl-Cl breaks to two Cl rad Propagation: Cl rad + alkane making Cl-H and alkane rad Alkane rad + Cl-Cl making alkane with one less H and Cl attached Chlorination of Higher Alkanes Cl2 with light heat # of signals is types of products Not very regioselectivity Bromination of Higher Alkanes Br2 with light heat Very regioselective Br goes to most sub C Radical Stability Allylic radical > 3 > 2 > 1 > me > vinyl =. Stereochemistry of radical Halogen Cl rad + alkane Cl & Br can be added to top or bottom on straight bond creating enantiomers or diasteromers Allylic Substitution If it is alkene + X2 at high concentration, low temp over a non polar solvent then it is a vicinal dihalide ( X to both previous alkene Cs) If it is alkene + X2 at low concentration, high temp then one X subs on sp3 C attached to double bond and the bond stays and HX is made

Oxidizing Agents

Substances that gain electrons and are reduced in a chemical reaction.

H2O2 (Hydrogen peroxide)

An example of an oxidizing agent used in various chemical reactions.

Reduction of Alkynes to Trans Alkenes

Involves the addition of Na and liquid NH3, resulting in H atoms added to opposite sides of the alkene.

H2 and Lindlar's catalyst

Used for the reduction of alkynes to cis alkenes, resulting in H atoms added to the same side.

Catalytic Hydrogenation

Process of reducing alkenes to alkanes using H2 and a catalyst, resulting in syn addition of hydrogen.

Stability of Alkenes

More substituted alkenes are more stable, with trans alkenes being more stable than cis.

Reduction of Alkyl Halides with LiAlH4

A method that replaces halogen (X) with hydrogen in an SN2 reaction.

Epoxidation of Alkenes

Conversion of alkenes to epoxides using peracids, which is stereospecific.

Oxidative Cleavage of Alkenes

Breaking double bonds to form carbonyls (aldehydes or ketones) using O3.

PCC Oxidation

A method that oxidizes alcohols to aldehydes without further oxidation to carboxylic acids.

Oxidation of Alcohols

The process of transforming primary alcohols into aldehydes and then to carboxylic acids.

Anti - 1,2 - dihydroxylation

The addition of hydroxyl groups to opposite sides of a double bond following epoxidation.

Radicals

Unpaired electrons that lead to reactions involving sigma and pi bonds.

Alkane Chlorination

A reaction where alkanes react with halogens (Cl2 or Br2) in an exothermic process.

Radical Stability

Ranking of radical stability from most to least stable, where allylic radicals are the most stable.

Allylic Chlorination

A reaction that adds Cl to an alkene under specific conditions, resulting in a vicinal dihalide.

Anti-Markovnikov Addition

Addition of HBr to alkenes with peroxide, where H attaches to the carbon with fewer H atoms.