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Questions and Answers
What is the main product formed when propene reacts with hydrogen bromide?
What is the main product formed when propene reacts with hydrogen bromide?
- (CH3)2CHBr
- CH3CH2CH2Br
- CH3CHBrCH3 (correct)
- All of the above
Which of the following is NOT a characteristic of the Finkelstein reaction?
Which of the following is NOT a characteristic of the Finkelstein reaction?
- It is used to prepare alkyl iodides.
- The reaction is driven by the precipitation of NaCl or NaBr.
- It involves the reaction of an alkyl chloride or bromide with NaI in dry acetone.
- It is an example of a SN1 reaction. (correct)
What is the primary driving force behind the Finkelstein reaction?
What is the primary driving force behind the Finkelstein reaction?
- The formation of a precipitate of NaCl or NaBr. (correct)
- The high reactivity of NaI in dry acetone.
- The liberation of heat during the reaction.
- The formation of a more stable carbocation intermediate.
Why is the addition of bromine in CCl4 to an alkene a useful test for the presence of a double bond?
Why is the addition of bromine in CCl4 to an alkene a useful test for the presence of a double bond?
Which of the following statements is TRUE about the free radical monochlorination of (CH3)2CHCH2CH3?
Which of the following statements is TRUE about the free radical monochlorination of (CH3)2CHCH2CH3?
What is the name of the product formed when bromine is added to an alkene?
What is the name of the product formed when bromine is added to an alkene?
Which of the following conditions would favor the formation of the more stable carbocation intermediate in the addition of hydrogen bromide to an alkene?
Which of the following conditions would favor the formation of the more stable carbocation intermediate in the addition of hydrogen bromide to an alkene?
Which of the following is the most likely product of the reaction between 2-methylpropene and hydrogen bromide?
Which of the following is the most likely product of the reaction between 2-methylpropene and hydrogen bromide?
In the synthesis of vic-dibromides, what is the primary role of the halogenating reagent?
In the synthesis of vic-dibromides, what is the primary role of the halogenating reagent?
What is the key principle that dictates the major product in an elimination reaction of a haloalkane, as described by Zaitsev's rule?
What is the key principle that dictates the major product in an elimination reaction of a haloalkane, as described by Zaitsev's rule?
How does Le Chatelier's principle apply to the Finkelstein reaction, where a primary alkyl halide is converted to an alkyl iodide using sodium iodide in acetone?
How does Le Chatelier's principle apply to the Finkelstein reaction, where a primary alkyl halide is converted to an alkyl iodide using sodium iodide in acetone?
In the halogenation of alkanes, what factor primarily determines the regioselectivity of the reaction, i.e., which carbon atom is most likely to be halogenated?
In the halogenation of alkanes, what factor primarily determines the regioselectivity of the reaction, i.e., which carbon atom is most likely to be halogenated?
Why is the attack of a nucleophile on a carbocation possible from either side of the plane?
Why is the attack of a nucleophile on a carbocation possible from either side of the plane?
Which statement best describes the formation of an alkene in an elimination reaction involving a haloalkane?
Which statement best describes the formation of an alkene in an elimination reaction involving a haloalkane?
What is the major product formed when 2-bromopentane undergoes dehydrohalogenation with alcoholic potassium hydroxide?
What is the major product formed when 2-bromopentane undergoes dehydrohalogenation with alcoholic potassium hydroxide?
Which of the following factors can influence the rate of an elimination reaction of a haloalkane?
Which of the following factors can influence the rate of an elimination reaction of a haloalkane?
Which method effectively leads to the formation of pure alkyl halides?
Which method effectively leads to the formation of pure alkyl halides?
As you move down the group of halogens, what is the trend observed in carbon-halogen bond lengths?
As you move down the group of halogens, what is the trend observed in carbon-halogen bond lengths?
What happens to the dipole moment as the size of the halogen atom increases?
What happens to the dipole moment as the size of the halogen atom increases?
Which carbon-halogen bond has the highest bond enthalpy?
Which carbon-halogen bond has the highest bond enthalpy?
Which of the following reactions primarily leads to vic-dibromides?
Which of the following reactions primarily leads to vic-dibromides?
How does Le Chatelier's Principle apply to the synthesis of haloalkanes?
How does Le Chatelier's Principle apply to the synthesis of haloalkanes?
Which reaction is known for substituting iodine in haloalkanes with another halogen?
Which reaction is known for substituting iodine in haloalkanes with another halogen?
What is a common misconception about the carbon-halogen bond's polarity?
What is a common misconception about the carbon-halogen bond's polarity?
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Study Notes
Addition Reactions of Alkenes
- Alkenes undergo addition reactions with hydrogen halides (HCl, HBr, HI) to convert into corresponding alkyl halides.
- Propene example shows that two products are formed, but one predominates due to Markovnikov’s rule.
Bromine Addition for Detection
- Addition of bromine in carbon tetrachloride (CCl4) is used to detect double bonds; the reddish-brown color of bromine disappears.
- The process results in the formation of vic-dibromides, which are colorless.
Monochlorination Isomers
- Free radical monochlorination of (CH3)2CHCH2CH3 yields several monochloro structural isomers:
- (CH3)2CHCH2CH2Cl
- (CH3)2CHCH(Cl)CH3
- (CH3)2C(Cl)CH2CH3
- CH3CH(CH2Cl)CH2CH3
Finkelstein Reaction
- Alkyl iodides can be synthesized by reacting alkyl chlorides or bromides with NaI in dry acetone.
- NaCl or NaBr precipitate, driving the reaction forward per Le Chatelier’s Principle.
Carbon-Halogen Bond Characteristics
- Halogen atoms are more electronegative than carbon, leading to polarized C-X bonds: carbon bears a partial positive charge, halogen bears a partial negative charge.
- Bond length increases from C-F to C-I due to the increasing size of halogen atoms.
Carbon-Halogen Bond Data
- Typical data for bond lengths, bond enthalpies, and dipole moments include:
- CH3–F: 139 pm, 452 kJ/mol, 1.847 Debye
- CH3–Cl: 178 pm, 351 kJ/mol, 1.860 Debye
- CH3–Br: 193 pm, 293 kJ/mol, 1.830 Debye
- CH3–I: 214 pm, 234 kJ/mol, 1.636 Debye
Preparation of Haloalkanes
- Haloalkanes can be made by replacing the hydroxyl group of an alcohol using concentrated halogen acids, phosphorus halides, or thionyl chloride.
- Thionyl chloride is preferred because it generates gaseous products (SO2 and HCl) that escape, leading to pure alkyl halides.
Elimination Reactions
- Heating haloalkanes with b-hydrogen atoms in alcoholic potassium hydroxide leads to elimination reactions, resulting in alkene formation.
- The elimination produces the major product according to Zaitsev’s rule, which states that the more substituted alkene is favored.
- Example: 2-bromopentane yields pent-2-ene as the major product due to greater alkyl group attachments on the double bond.
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