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Questions and Answers
What type of addition occurs when halogens, such as Cl and Br, are added to a double bond in the absence of light?
What type of addition occurs when halogens, such as Cl and Br, are added to a double bond in the absence of light?
In the hydration of alkenes to form alcohol, what role does an acid catalyst like H2SO4 play in the reaction?
In the hydration of alkenes to form alcohol, what role does an acid catalyst like H2SO4 play in the reaction?
What effect does the presence of an electron-withdrawing group have on the addition of electrophiles to an alkene?
What effect does the presence of an electron-withdrawing group have on the addition of electrophiles to an alkene?
Why is acid-catalyzed hydration of alkenes rarely used in alcohol preparation?
Why is acid-catalyzed hydration of alkenes rarely used in alcohol preparation?
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What is a characteristic feature of the addition of water to alkenes?
What is a characteristic feature of the addition of water to alkenes?
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What is the primary result of using hot alkaline KMnO4 on 2-alkenes?
What is the primary result of using hot alkaline KMnO4 on 2-alkenes?
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In which condition does the halogenation of alkenes take place via a free radical mechanism?
In which condition does the halogenation of alkenes take place via a free radical mechanism?
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What effect does heating have on the reaction of 1-propene with KMnO4/OH?
What effect does heating have on the reaction of 1-propene with KMnO4/OH?
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What is indicated if the brown color of bromine disappears upon adding a hydrocarbon?
What is indicated if the brown color of bromine disappears upon adding a hydrocarbon?
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Which reagent is used in the Bayer test for unsaturation?
Which reagent is used in the Bayer test for unsaturation?
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What type of reaction occurs when alkenes with disubstituted carbon atoms are oxidized?
What type of reaction occurs when alkenes with disubstituted carbon atoms are oxidized?
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Which of the following processes results in a substitution reaction for alkenes?
Which of the following processes results in a substitution reaction for alkenes?
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What is formed when an alkene reacts with a peroxyacid?
What is formed when an alkene reacts with a peroxyacid?
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What is oxidized to CO2 and H2O when 1-alkenes undergo oxidation with KMnO4?
What is oxidized to CO2 and H2O when 1-alkenes undergo oxidation with KMnO4?
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What is the result of oxidative cleavage of an alkene using warm concentrated acidic KMnO4?
What is the result of oxidative cleavage of an alkene using warm concentrated acidic KMnO4?
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Which statement about oxidative cleavage of alkenes is true?
Which statement about oxidative cleavage of alkenes is true?
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Which type of diols are produced from the reaction of alkenes with cold, dilute aqueous potassium permanganate?
Which type of diols are produced from the reaction of alkenes with cold, dilute aqueous potassium permanganate?
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What happens to disubstituted carbons during oxidative cleavage?
What happens to disubstituted carbons during oxidative cleavage?
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What key characteristic differentiates the ionic addition reaction from the free radical halogenation mechanism?
What key characteristic differentiates the ionic addition reaction from the free radical halogenation mechanism?
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Which statement about the oxidative cleavage process is FALSE?
Which statement about the oxidative cleavage process is FALSE?
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What is the main characteristic of a trans or anti diol formation?
What is the main characteristic of a trans or anti diol formation?
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Study Notes
Oxidation with σ bond cleavage:
- Hot, alkaline KMnO4 oxidizes 2-alkenes into acid salts
- Terminal CH2 in 1-alkene is oxidized into CO2 and H2O
- Alkenes with disubstituted C atom of a double bond are oxidized into ketones
Halogenation of alkenes:
- Halogenation of alkenes at high temperature in the gaseous state proceeds by a free radical mechanism resulting in substitution reaction.
- Ionic addition reaction occurs at low temperatures and in the absence of light and generally in the liquid phase.
Oxidation Reaction:
- Oxidation to 1,2-diols (vicinal diols) (glycols) where the Pi bond is only broken with the formation of 2 new σ bonds bearing OH groups
- Syn-diols are formed using cold, dilute aqueous potassium permanganate followed by hydrolysis with base (Bayer test for unsaturation)
- Trans-diols (epoxide formation) are formed when an alkene reacts with a peroxyacid (peroxybenzoic) to form an epoxide followed by acid hydrolysis
Epoxide Formation:
- Nobel Prize in Chemistry 2001 was awarded to Karl Sharpless for his work in this field
Oxidative Cleavage:
- Both the pi and sigma bonds break. C=C becomes C=O
- Using warm concentrated acidic KMnO4
- Used to determine the position of a double bond in an unknown
- Permanganate is a strong oxidizing agent
- Glycol initially formed is further oxidized
- Disubstituted carbons become ketones
- Monosubstituted carbons become carboxylic acids
- Terminal =CH2 becomes CO2.
- More general Markovnikov’s Rule: in an electrophilic addition to an alkene, the electrophile adds in such a way as to form the most stable intermediate (carbocation)
- HI> HBr> HCl add to alkenes to form Markovnikov products
Anti-Markovnikov addition:
- Presence of an electron-withdrawing (-I effect) group adjacent to the olefinc (double bond) e,g CF3 , NO2 ,C≡N and COOH make the addition anti-Markovnikov
Addition of Water to Alkenes:
- Hydration of Alkenes results in alcohol formation
- The reaction is the reverse of dehydration of alcohol
- Use very dilute solutions of H2SO4 or H3PO4 to drive equilibrium toward hydration (acid catalyst reaction)
Acid catalyst hydration of alkene
- Is seldom used in alcohol preparation due to the possibility of rearrangement
Addition of Halogens (unsaturation test):
- Cl2, Br2 (in CCl4) add to a double bond in the absence of light and at room temperature to form a vicinal dibromide
- Anti addition, so reaction is stereospecific
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Description
Explore the fascinating world of organic chemistry focusing on alkenes and their reactions. This quiz covers oxidation processes, halogenation, and the formation of diols and epoxides. Test your understanding of these key concepts in organic reactions.
