Ochem Reactions

ALKENE: Hydrohalogenation — reagents?

HX (HCl, HBr, or HI).

ALKENE: HX adds to an alkene — product?

Alkyl halide; X goes to the more substituted alkene carbon (Markovnikov).

ALKENE: Hydrohalogenation — stereochemistry and intermediate?

No stereochemical preference; carbocation can rearrange.

ALKENE: Modified hydrobromination — reagents?

HBr, ROOR (peroxides).

ALKENE: HBr + ROOR — product and regiochemistry?

Alkyl bromide; Br on the less substituted carbon (anti-Markovnikov).

ALKENE: Modified hydrobromination — key limitations?

Only HBr shows the peroxide effect; no carbocation/rearrangement; no stereopreference.

ALKENE: Acid-catalyzed hydration — reagents?

H3O+ (water and acid, often H2SO4/H2O).

ALKENE: Acid-catalyzed hydration — product?

Markovnikov alcohol: OH adds to the more substituted carbon.

ALKENE: Acid-catalyzed hydration — intermediate and stereochemistry?

Carbocation; rearrangements possible; no stereopreference.

ALKENE: Acid-catalyzed ether formation — reagents?

ROH (alcohol) and H+.

ALKENE: Acid-catalyzed ether formation — product?

Ether (R-O-R); OR adds Markovnikov to the more substituted carbon.

ALKENE: Acid-catalyzed ether formation — key caution?

Carbocation rearrangements can occur; no stereopreference.

ALKENE: Oxymercuration-demercuration — reagents?

1. Hg(OAc)2, H2O; 2. NaBH4.

ALKENE: Oxymercuration-demercuration — product?

Markovnikov alcohol (OH on more substituted carbon).

ALKENE: Oxymercuration-demercuration — special advantage?

No free carbocation or rearrangement; overall no stereopreference.

ALKENE: Modified oxymercuration-demercuration — reagents?

1. Hg(OAc)2, ROH; 2. NaBH4.

ALKENE: Modified oxymercuration-demercuration — product?

Markovnikov ether (OR on more substituted carbon).

ALKENE: Modified oxymercuration-demercuration — rearrangement?

No carbocation rearrangement; overall no stereopreference.

ALKENE: Halogenation — reagents?

Br2 or Cl2 in CCl4 (or CH2Cl2).

ALKENE: X2 addition — product?

Vicinal dihalide: one halogen on each of the two alkene carbons.

ALKENE: Halogenation — stereochemistry?

Anti addition; nonparticipating solvent CCl4 or CH2Cl2.

ALKENE: Halohydrin formation — reagents?

Br2 or Cl2 with H2O.

ALKENE: Halohydrin formation — product and regiochemistry?

Halohydrin: OH on more substituted carbon; X on less substituted carbon.

ALKENE: Halohydrin formation — stereochemistry?

Anti addition of OH and X.

ALKENE: Haloether formation — reagents?

Br2 or Cl2 with ROH (alcohol).

ALKENE: Haloether formation — product and regiochemistry?

Haloether: OR on more substituted carbon; X on less substituted carbon.

ALKENE: Haloether formation — stereochemistry?

Anti addition of OR and X.

ALKENE: Hydroboration-oxidation — reagents?

1. BH3, THF; 2. H2O2, OH-.

ALKENE: Hydroboration-oxidation — product?

Anti-Markovnikov alcohol: OH on less substituted carbon.

ALKENE: Hydroboration-oxidation — stereochemistry?

Syn addition of H and OH.

ALKENE: Hydroboration-oxidation — other boranes?

BH3 can be replaced with R2BH or 9-BBN.

ALKENE: Syn dihydroxylation — reagents?

1. OsO4, pyridine; 2. NaHSO3, H2O.

ALKENE: Syn dihydroxylation — product?

Syn (cis) vicinal diol: two OH groups added to the same face.

ALKENE: Syn dihydroxylation — alternate reagents?

OsO4/NMO; OsO4/tBuOOH; or cold KMnO4/NaOH.

ALKENE: Epoxide formation using a peroxyacid — reagents?

RCO3H (a peroxyacid), commonly mCPBA.

ALKENE: RCO3H or mCPBA — product?

Epoxide (three-membered ring containing oxygen).

ALKENE: Peroxyacid epoxidation — stereochemistry?

Stereospecific syn oxygen transfer; alkene geometry is retained.

ALKENE: Epoxide formation via halohydrin — reagents?

1. X2, H2O; 2. NaOH (or another strong base).

ALKENE: Epoxide formation via halohydrin — product?

Epoxide, formed by intramolecular ring closure of a halohydrin.

ALKENE: Halohydrin-to-epoxide — why is base added?

Base makes an alkoxide, which displaces X intramolecularly to close the ring.

ALKENE: Anti dihydroxylation — reagents?

1. RCO3H (such as mCPBA); 2. H3O+.

ALKENE: Anti dihydroxylation — product?

Anti (trans) vicinal diol: OH groups on opposite faces.

ALKENE: Anti dihydroxylation — two steps?

Step 1 makes an epoxide; step 2 opens it with acidified water.

ALKENE: Catalytic hydrogenation — reagents?

H2 with Pt, Pd, Pd/C, or Ni.

ALKENE: Catalytic hydrogenation — product?

Alkane (C=C becomes C-C by adding H2).

ALKENE: Catalytic hydrogenation — stereochemistry and limitation?

Syn addition; typical conditions do not reduce benzene/arene C=C.

ALKENE: Ozonolysis (reductive) — reagents?

1. O3; 2. Zn, H+ or (CH3)2S.

ALKENE: Reductive ozonolysis — what happens?

C=C is cleaved into two carbonyl compounds (aldehydes and/or ketones).

ALKENE: Ozonolysis carbon with 0 hydrogens — product?

Ketone.

ALKENE: Ozonolysis carbon with 1 hydrogen — product?

Aldehyde.

ALKENE: Ozonolysis carbon with 2 hydrogens — product?

Formaldehyde (HCHO).

ALKYNE: Hydrohalogenation — reagents?

1 or 2 equivalents HX (HCl, HBr, or HI).

ALKYNE: 1 equivalent HX — product?

Markovnikov vinyl halide (alkene with X on the more substituted carbon).

ALKYNE: 2 equivalents HX — product?

Geminal dihalide: both halogens on the same carbon.

ALKYNE: HX hydrohalogenation — stereochemistry?

No stereochemical preference.

ALKYNE: Modified hydrobromination — reagents?

HBr with ROOR (peroxides).

ALKYNE: 1 equivalent HBr/ROOR — product?

Anti-Markovnikov vinyl bromide; often an E/Z mixture.

ALKYNE: 2 equivalents HBr/ROOR — product?

Dibromoalkane; the sheet shows bromines on adjacent carbons.

ALKYNE: Peroxide hydrohalogenation — works with which HX?

HBr only; not HCl or HI.

ALKYNE: Halogenation — reagents?

1 or 2 equivalents Br2 or Cl2.

ALKYNE: 1 equivalent X2 — product?

Trans (E) vicinal dihaloalkene from anti addition.

ALKYNE: 2 equivalents X2 — product?

Tetrahaloalkane: two X atoms on each former triple-bond carbon.

ALKYNE: Acid-catalyzed hydration — reagents?

H2O, H2SO4, HgSO4.

ALKYNE: Acid-catalyzed hydration — final product?

Ketone (terminal alkynes give methyl ketones).

ALKYNE: Acid-catalyzed hydration — intermediate?

Markovnikov enol, which tautomerizes into a ketone.

ALKYNE: Why use HgSO4 in acid hydration?

Required catalyst for terminal alkynes; can also be used for internal alkynes.

ALKYNE: Hydroboration-oxidation — reagents?

1. R2BH, THF; 2. H2O2, OH-.

ALKYNE: Terminal hydroboration-oxidation — final product?

Aldehyde (anti-Markovnikov hydration after tautomerization).

ALKYNE: Hydroboration-oxidation — intermediate?

Anti-Markovnikov enol, then tautomerization to a carbonyl.

ALKYNE: Hydroboration-oxidation — suitable boranes?

9-BBN or disiamylborane (R2BH).

ALKYNE: Hydroboration — why avoid BH3 on terminal alkynes?

BH3 should not be used; use bulky borane such as 9-BBN instead.

ALKYNE: Full catalytic hydrogenation — reagents?

Excess H2 with Pt, Pd, Pd/C, or Ni.

ALKYNE: Full catalytic hydrogenation — product?

Alkane (triple bond completely reduced).

ALKYNE: Full hydrogenation — is excess H2 assumed?

Yes; the sheet says always assume excess.

ALKYNE: Lindlar reduction — reagents?

H2 with Lindlar's catalyst (poisoned catalyst).

ALKYNE: Lindlar reduction — product?

Cis (Z) alkene; stops at the double bond.

ALKYNE: Lindlar reduction — stereochemistry?

Syn addition of H2.

ALKYNE: Dissolving metal reduction — reagents?

Na or Li in liquid NH3, about -78°C.

ALKYNE: Dissolving metal reduction — product?

Trans (E) alkene; stops at the double bond.

ALKYNE: Dissolving metal reduction — stereochemistry?

Anti addition of hydrogen.

ALKYNE: Dissolving metal reduction — caution?

Avoid using on terminal alkynes (per the sheet).

ALKYNE: Ozonolysis — reagents?

1. O3; 2. H2O.

ALKYNE: Internal alkyne ozonolysis — products?

Two carboxylic acids after cleavage of the C≡C bond.

ALKYNE: Terminal alkyne ozonolysis — products?

One carboxylic acid plus CO2.

ALKYNE: Chain extension — two reaction steps?

1. NaNH2 in NH3; 2. primary alkyl halide R-X (sheet: R-Br).

ALKYNE: What does NaNH2 do to a terminal alkyne?

Removes terminal H to form an acetylide anion (C≡C-).

ALKYNE: What does acetylide + primary R-Br form?

A longer carbon chain with a C-C bond; internal alkyne after alkylation.

ALKYNE: Chain extension — key constraints?

Step 1 at about -78°C; Step 2 uses a primary (1°) alkyl halide.

COMPARE: Alkene Markovnikov alcohol WITHOUT rearrangement?

Oxymercuration-demercuration: Hg(OAc)2/H2O, then NaBH4.

COMPARE: Alkene anti-Markovnikov alcohol?

Hydroboration-oxidation: BH3/THF, then H2O2/OH-.

COMPARE: Syn diol vs anti diol reagents?

Syn: OsO4 (or cold KMnO4); anti: RCO3H, then H3O+.

COMPARE: Cis vs trans alkene from an alkyne?

Cis/Z: H2/Lindlar; trans/E: Na or Li/NH3(l).

COMPARE: Terminal alkyne → methyl ketone vs aldehyde?

Methyl ketone: H2O/H2SO4/HgSO4; aldehyde: R2BH then H2O2/OH-.

COMPARE: Alkene peroxide effect vs HX alone?

HBr/ROOR: anti-Markovnikov; HX alone: Markovnikov.