Organic Chemistry: Alkenes and Alkynes

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Questions and Answers

What suffix is commonly used in the nomenclature of alkenes?

  • -yne
  • -ane
  • -ene (correct)
  • -ol

Electrophilic addition of H2O to alkenes is always anti-addition.

False (B)

What is the regioselectivity when adding HBr to an alkene?

Markovnikov

In the bromination of alkenes, a ______ ion is formed as an intermediate.

<p>bromonium</p> Signup and view all the answers

Match the reagents with their resulting products in electrophilic addition to alkenes:

<p>HBr = H+ and Br- Br2/CCl4 = Br+ and Br- H3O+ = H+ and OH- H2/catalyst = H and H</p> Signup and view all the answers

Which reaction leads to syn addition?

<p>H2/catalyst (B)</p> Signup and view all the answers

Electrophilic addition reactions can involve carbocation rearrangement.

<p>True (A)</p> Signup and view all the answers

What is the result of the hydroboration-oxidation reaction on an alkene?

<p>Anti-Markovnikov addition of alcohol</p> Signup and view all the answers

Using ______ as a reagent provides an anti addition mechanism.

<p>Br2/CCl4</p> Signup and view all the answers

Match the reagent with its type of selectivity:

<p>H2/catalyst = Syn addition HBr = Markovnikov Br2/H2O = Markovnikov BH3.THF = Anti-Markovnikov</p> Signup and view all the answers

What is the condition required for oxidative cleavage of alkenes using ozonolysis?

<p>O3 at -78°C (A)</p> Signup and view all the answers

Anti-Markovnikov addition occurs with the presence of a radical initiator.

<p>True (A)</p> Signup and view all the answers

What is the product formation for syn addition using RCO3H (MCPBA)?

<p>OH and OH</p> Signup and view all the answers

Under reducing conditions, the products formed from oxidative cleavage yield ___ chiral centers.

<p>none</p> Signup and view all the answers

Match the oxidative conditions with their appropriate method:

<p>Ozone = Ozonolysis KMnO4 (hot, concentrated) = Oxidative cleavage KMnO4 (cold, dilute) = Hydroxylation H2O2 = Oxidation</p> Signup and view all the answers

Which reagent is used in syn hydroxylation of alkenes?

<p>KMnO4 (cold, dilute) (C)</p> Signup and view all the answers

Both syn and anti addition products from alkene reactions are chiral.

<p>False (B)</p> Signup and view all the answers

What is the typical number of chiral centers when using OsO4 for syn addition?

<p>2</p> Signup and view all the answers

In anti-addition reactions, the usual number of products formed is ___.

<p>2</p> Signup and view all the answers

What is the result of oxidative cleavage under reducing conditions?

<p>No chiral centers (C)</p> Signup and view all the answers

Match the electrophilic addition reagents to their added components:

<p>HBr (or HCl, HI) = H+ and Br- H3O+ = H+ and OH- Br2/CCl4 = Br+ and Br- (1) BH3.THF = H+ and OH-</p> Signup and view all the answers

Match the reagents with their regioselectivity:

<p>HBr (or HCl, HI) = Markovnikov Br2/H2O = Markovnikov (1) Hg(OAc)2, H2O = Markovnikov (1) BH3.THF = Anti-Markovnikov</p> Signup and view all the answers

Match the reagents with their intermediate types:

<p>Br2/CCl4 = bromonium ion (1) Hg(OAc)2, H2O = mercurinium ion H2/catalyst = - H3O+ = carbocation</p> Signup and view all the answers

Match the reagent with its type of stereochemistry:

<p>Br2/CCl4 = Anti (1) BH3.THF = Syn (1) Hg(OAc)2, ROH = Anti H2/catalyst = Syn</p> Signup and view all the answers

Match the reagents with potential rearrangements:

<p>HBr (or HCl, HI) = Possible (1) Hg(OAc)2, H2O = No H2/catalyst = No (1) BH3.THF = No</p> Signup and view all the answers

Match the reagent to its product nature:

<p>Br2/H2O = H+ and OH- HBr/ROOR (peroxide) = H and Br (2) NaBH4 = Reducing agent H3O+ = Hydration product</p> Signup and view all the answers

Match the reagents with their used solvents or catalysts:

<p>Br2/CCl4 = Non-polar solvent H2/catalyst = Pd/C, Pt/C, or Ni H3O+ = Water (1) Hg(OAc)2, ROH = Alcohol</p> Signup and view all the answers

Match the reagents with their final product specificity:

<p>HBr (or HCl, HI) = Add H and halogen (1) Hg(OAc)2, ROH = Markovnikov product H2/catalyst = Alkane product (1) BH3.THF = Anti-Markovnikov alcohol</p> Signup and view all the answers

Match the reaction conditions with the type of addition they produce:

<p>RCO3H (MCPBA) = Syn addition (1) OsO4, (2) H2O2 = Syn addition KMnO4 (cold, dilute)/ OH- = Syn addition (1) O3, (2) (CH3)2S = Reductive cleavage</p> Signup and view all the answers

Match the reagents with their respective outcomes in oxidative cleavage of alkenes:

<p>O3, -78°C = Produces carbonyl compounds KMnO4 (hot, concentrated)/OH- = Oxidative cleavage H2O2 = Oxidative cleavage Zn/H2O = Reductive cleavage</p> Signup and view all the answers

Match the type of mechanism with its characteristic addition:

<p>Anti-Markovnikov = Radical addition Syn addition = Bicyclic intermediates Anti addition = Non-superimposable products Syn addition with OsO4 = Formation of 2 chiral centers</p> Signup and view all the answers

Match the products with the usual number of chiral centers formed:

<p>0 chiral centers = None 1 chiral center = 2 products 2 chiral centers = Syn addition 4 products = None</p> Signup and view all the answers

Match the reagents with their specific types of addition:

<p>RCO3H (MCPBA) = Anti addition OsO4 = Syn addition KMnO4 (cold, dilute) = Syn addition H3O+ = Acidic hydration</p> Signup and view all the answers

Match the oxidative cleavage conditions with their type:

<p>O3 followed by H2O2 = Oxidizing conditions KMnO4 (hot, concentrated) = Oxidizing conditions Zn in acid = Reducing conditions (1) O3, (2) (CH3)2S = Reducing conditions</p> Signup and view all the answers

Match the addition mechanism with their reagent:

<p>Radical = HBr with peroxide Syn addition = OsO4 Anti addition = RCO3H Hydration = H3O+</p> Signup and view all the answers

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Study Notes

Alkenes Nomenclature

  • Alkenes are identified by the suffix "-ene."
  • Configuration designated as E/Z specifies the relative positioning of substituents around the double bond.

Electrophilic Addition Reactions

  • Various reagents can add to alkenes via electrophilic addition, with each reaction having different characteristics.

Reagent Types and Characteristics

  • HBr, HCl, HI

    • Adds H+ and Br-.
    • Follows Markovnikov's rule for regioselectivity.
    • Possible carbocation rearrangement.

  • H3O+

    • Produces H+ and OH-.
    • Also follows Markovnikov's rule with rearrangement possible.

  • H2 and ROH

    • Adds H+ and OR- conforming to Markovnikov's rule with possible rearrangement.

  • Br2/CCl4 or Cl2

    • Adds Br+ and Br- or Cl+ and Cl-.
    • Anti addition (trans) through formation of a bromonium or chloronium ion.
    • No rearrangement possible.

  • Br2/H2O and Cl2/H2O

    • Adds Br+ and OH- or Cl+ and OH-.
    • Markovnikov's rule applies, with anti addition.

  • Br2/ROH and Cl2/ROH

    • Produces Br+ and OR- or Cl+ and OR-.
    • Follows Markovnikov's rule with anti addition.

  • (1) Hg(OAc)2, H2O / (2) NaBH4

    • Introduces H+ and OH-.
    • Adheres to Markovnikov's rule with anti addition.

  • (1) BH3.THF / (2) H2O2, OH-, H2O

    • Forms H+ and OH-.
    • Anti-Markovnikov addition resulting in syn stereochemistry.

  • H2/catalyst (Pd/C, Pt/C, Ni)

    • Hydrogenation resulting in syn addition of H and H.

  • HBr/ROOR (peroxide)

    • Produces anti-Markovnikov addition of H and Br.
    • Involves a radical mechanism.

  • RCO3H (MCPBA)

    • Creates O via syn addition.

  • (1) RCO3H (MCPBA) / (2) H3O+

    • Yields OH and OH through anti addition.

  • (1) OsO4 / (2) H2O2

    • Generates OH and OH through syn addition.

  • KMnO4 (cold, dilute)/OH-

    • Adds OH and OH in syn fashion.

Chiral Centers and Products

  • No chiral centers lead to 1 product.
  • One chiral center generates 2 products.
  • Two chiral centers can create 2 syn products or 2 anti products, leading to a total of 4 products in syn or anti scenarios.

Oxidative Cleavage of Alkenes

  • Reducing Conditions:

    • O3 followed by (CH3)2S or Zn/H2O cleaves alkenes.

  • Oxidizing Conditions:

    • O3 followed by H2O2 or KMnO4 (hot, concentrated)/OH- or with H3O+ achieves oxidative cleavage.

Alkenes Nomenclature

  • Alkenes are identified by the suffix "-ene."
  • Configuration designated as E/Z specifies the relative positioning of substituents around the double bond.

Electrophilic Addition Reactions

  • Various reagents can add to alkenes via electrophilic addition, with each reaction having different characteristics.

Reagent Types and Characteristics

  • HBr, HCl, HI

    • Adds H+ and Br-.
    • Follows Markovnikov's rule for regioselectivity.
    • Possible carbocation rearrangement.

  • H3O+

    • Produces H+ and OH-.
    • Also follows Markovnikov's rule with rearrangement possible.

  • H2 and ROH

    • Adds H+ and OR- conforming to Markovnikov's rule with possible rearrangement.

  • Br2/CCl4 or Cl2

    • Adds Br+ and Br- or Cl+ and Cl-.
    • Anti addition (trans) through formation of a bromonium or chloronium ion.
    • No rearrangement possible.

  • Br2/H2O and Cl2/H2O

    • Adds Br+ and OH- or Cl+ and OH-.
    • Markovnikov's rule applies, with anti addition.

  • Br2/ROH and Cl2/ROH

    • Produces Br+ and OR- or Cl+ and OR-.
    • Follows Markovnikov's rule with anti addition.

  • (1) Hg(OAc)2, H2O / (2) NaBH4

    • Introduces H+ and OH-.
    • Adheres to Markovnikov's rule with anti addition.

  • (1) BH3.THF / (2) H2O2, OH-, H2O

    • Forms H+ and OH-.
    • Anti-Markovnikov addition resulting in syn stereochemistry.

  • H2/catalyst (Pd/C, Pt/C, Ni)

    • Hydrogenation resulting in syn addition of H and H.

  • HBr/ROOR (peroxide)

    • Produces anti-Markovnikov addition of H and Br.
    • Involves a radical mechanism.

  • RCO3H (MCPBA)

    • Creates O via syn addition.

  • (1) RCO3H (MCPBA) / (2) H3O+

    • Yields OH and OH through anti addition.

  • (1) OsO4 / (2) H2O2

    • Generates OH and OH through syn addition.

  • KMnO4 (cold, dilute)/OH-

    • Adds OH and OH in syn fashion.

Chiral Centers and Products

  • No chiral centers lead to 1 product.
  • One chiral center generates 2 products.
  • Two chiral centers can create 2 syn products or 2 anti products, leading to a total of 4 products in syn or anti scenarios.

Oxidative Cleavage of Alkenes

  • Reducing Conditions:

    • O3 followed by (CH3)2S or Zn/H2O cleaves alkenes.

  • Oxidizing Conditions:

    • O3 followed by H2O2 or KMnO4 (hot, concentrated)/OH- or with H3O+ achieves oxidative cleavage.

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