CHEM 2443 Key Terms & Definitions for Exam 2 Review

Dehydrohalogenation

Use strong base to deprotonate to make alkene (K+ takes Br, OH takes H)

Dehydration

Use strong acid to make alkene (strong acid protonates OH, water takes H+ from nearby C to form C=C)

Reduction (which mechanism)

Gaining electron density for carbon (hydrogenation)

Oxidation (which mechanisms 5)

Losing electron density for carbon

(halogenation, halohydrination, epoxidation, dihydroxylation with OsO4, ozonolysis)

(anti or syn/trans or cis/mark or not)

give species needed/catalysts

Halogenation

Anti/trans/mark - bromonium

Alkene + X2 (halogen) --> alkanes with halogen

Halohydrination

Anti/trans/mark - bromonium

Alkene + X2 + H2O (DMSO) --> alkane alcohol

Halogen Nu in first attack, water Nu in second attack; extra deprotonation step)

Acid catalyzed hydration (a/chiral alkene makes...)

Anti/trans/mark

Alkene + H2O --H3O+--> alkane alcohol

Chiral alkene = chiral products; achiral alkene = racemic)

Carbocation rearrangement

Oxymercuration-demurcuration hydration

Anti/trans/mark

Alkene + HgOAC +H2O -->NaBH4--> alkane alcohol

step 1: similar to bromonium formation

step 2: OH addition follows mark and deprotonation

step 3: NaBH4 swaps HgOAC for H

No carbocations rearrangement

Hydroboration

Syn/cis/no mark (SN1 - one step)

Alkene + BH3 -+ THF -> oraganoborane --> H2O2 +NaOH +H2O --> alkane alcohol

(steric crowding relevant because no carbocation forms so BH2 adds to the less substituted C)

Hydrogenation

Syn/cis/mark does not apply)

Alkene + H2 --> Pd/C (metal catalyst) --> alkane

Epoxidation using peroxyacids

Anti/trans/mark

Alkene + mCPBA --> (CH2Cl) --> epoxide

Epoxidation using halohydrins

Anti/trans/mark

Alkene + Cl2 (halogen) + H2O --> alkane

Alkane int + NaOH --> alkane + H2O + NaCl

Epoxidation to make 1,2-diols (2 OHs)

Anti/trans/mark

Alkene --> epoxide

Epoxide + H3O+ --> int

H2O (Nu) then deprotonate --> alkane diol

Dihydroxylation (no epoxidation)

Syn/cis

Alkene + OsO4 --> int. --> NaHSO3 + H2O --> alkane 1,2-diol

Ozonlysis

Alkene + O3 --> ozonide + H2O + Zn --> 2 alkenes

-tetrasubstituted alkenes = 2 ketons (C=O)

-disubstituted alkenes = 2 aldehydes (HC=O)

Oxidation of alkene via KMnO4

Alkene + KMnO4 + OH- + heat --> ketone + carboxylate

- at least one C on the alkene must have H attactched

- monosubstitued side turns into carboxylic acid

- disubstituted side turns into ketone

Oxidation of alkene vis 1,2-diols with HIO4

1,2-diol + HIO4 --> int. --> carbonyl

(H removed to form C=O)

Cyclopropane synthesis using alkenes/carbenes

Alkene + carbene (sp2) --> cyclopropane

CHCl3 + OH- --> CCl2 (carbene)

Carbene: no formal charge but missing electron pair

Simmons-smith

Alkene + CH2I2 + Zn(Cu) --> cyclopropane

Alkyne hydration by oxymercuration

mark

-enol formed spontaneously convert to ketone

Alkyne reduction by Pd/Pt hydrogenation (Metal/Lindlar/Li)

H2 + metal catalyst --> alkane

H2 + lindlar catalyst --> alkene

Lindlar --> cis

Lithium --> trans

Alkyne hydration by hydroboration

Mark does not apply

Internal alkynes - both monosubstituted so no regioselectivity, forms enol —> ketone

Terminal alkynes - adds OH to the less bulky end, forms enol —> aldehyde

Alkyne synthesis by elimination

2 dehydrohalogenation reaction of alkane to form alkyne

Or

1 dehydrohalogenation reaction with strong base of alkene to form alkyne