Page 5 Flashcards
What is the first step in drawing the product of dehydrohalogenation?
A: Identify the α-carbon, which is bonded to the leaving group (halogen, X).
How do you identify the β-carbons in dehydrohalogenation?
A: Locate the carbons adjacent to the α-carbon and ensure they have at least one hydrogen atom (β-hydrogens).
What happens to the elements H and X during dehydrohalogenation?
A: They are removed from the α- and β-carbons, respectively, forming a π bond between the two carbons.
What is the product of dehydrohalogenation
of 2-bromo-2-methylpropane with NaOH?
A: The alkene formed is CH₂=C(CH₃)₂.
How many β-carbons are there in 2-bromo-2-methylpropane?
A: Three identical β-carbons, all leading to the same product.
What type of alkenes are formed from 2-bromobutane using K⁺OC(CH₃)₃ as the base?
A: Two constitutional isomers are formed: 1-butene (CH₂=CHCH₂CH₃) and 2-butene (CH₃CH=CHCH₃).
Why do multiple products form during dehydrohalogenation of 2-bromobutane?
A: There are two different β-carbons (β₁ and β₂), each capable of forming a double bond with the α-carbon.
Which product is favored when a bulky base like potassium tert-butoxide is used in dehydrohalogenation?
A: The less substituted alkene (Hofmann product) is favored due to steric hindrance.
What determines the regioselectivity of dehydrohalogenation products?
A: The base size and the stability of the potential alkene products (more substituted alkenes are generally more stable).
What is the major product of dehydrohalogenation of 2-bromobutane with a smaller base like NaOH?
A: The more substituted alkene (Zaitsev product), 2-butene, is the major product.
