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Alkenes and Alkynes Summary
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Alkenes and Alkynes Summary
Alkenes and Alkynes Summary
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1
Question
What representations of ethylene (C2H4) are shown in the chapter summary?
Answer
Lewis structure; 3D ball-and-stick; molecular orbital diagram
2
Question
What does the Lewis structure illustrate for ethylene?
Answer
Single bonds between C and H; carbon–carbon connection
3
Question
In the 3D ball-and-stick model, how are atoms colored?
Answer
Hydrogen white, carbon black
4
Question
What bonding features does the molecular orbital diagram reveal for ethylene?
Answer
Hybridization; π bond from unhybridized orbitals; σ bond from sp2 orbitals
5
Question
What is geometric isomerism in 2-butene (C4H8)?
Answer
Cis-trans (geometric) isomers due to restricted rotation around C=C
6
Question
Why can cis- and trans-2-butene exist, but not with a single bond?
Answer
Double bond prevents rotation; single bond allows rotation
7
Question
Describe cis-2-butene.
Answer
Terminal groups on same side of C=C (cis)
8
Question
Describe trans-2-butene.
Answer
Terminal groups on opposite sides of C=C (trans)
9
Question
What does CIP prioritize when assigning E/Z configuration?
Answer
Atomic number of atoms attached to the double bond
10
Question
What are the E and Z configurations in alkenes?
Answer
E: highest priorities opposite; Z: highest priorities same
11
Question
What does the term E stand for in E/Z notation?
Answer
Entgegen (opposite)
12
Question
What does the term Z stand for in E/Z notation?
Answer
Zusammen (together)
13
Question
What is syn addition?
Answer
Addition to same side of double bond
14
Question
What is anti addition?
Answer
Addition to opposite sides of double bond
15
Question
What type of reaction is hydrogenation of cyclohexene?
Answer
Electrophilic addition with H2 and metal catalyst; yields cyclohexane
16
Question
What rule governs regioselectivity in hydrohalogenation of cyclohexene?
Answer
Markovnikov's rule (H adds to more substituted carbon)
17
Question
Why is cyclohexene considered symmetrical in hydrohalogenation?
Answer
Both ends of the double bond are equivalent
18
Question
What are the three types of electrophilic addition reactions to alkenes described?
Answer
Carbocation pathway; cyclic intermediate; four-centered transition state (hydroboration-oxidation)
19
Question
What happens in Type 1 electrophilic addition to alkenes?
Answer
Protic acid adds via carbocation intermediate
20
Question
What characterizes Type 2 electrophilic addition to alkenes?
Answer
Halogen or H2 with cyclic intermediate
21
Question
What characterizes Type 3 electrophilic addition to alkenes?
Answer
Hydroboration-oxidation via four-centered transition state
22
Question
What defines an alkyne according to the module content?
Answer
Carbon–carbon triple bond (one σ and two π bonds)
23
Question
What is the geometry of an internal alkyne?
Answer
Linear geometry with 180° bond angle
24
Question
Where is the triple bond located in an internal alkyne?
Answer
Within the carbon chain, bonded to two carbons
25
Question
What does geminal dichloride refer to?
Answer
Two chlorine atoms bonded to the same carbon
26
Question
What is a dihalide?
Answer
Molecule with two halogen atoms
27
Question
In alkynes, what is hydration across the triple bond likely to form?
Answer
A ketone (not an alcohol)
28
Question
What happens to the triple bond during hydration of alkynes?
Answer
Triple bond is broken; new bonds form to yield carbonyl compound
29
Question
What is tautomerization in the context of alkynes?
Answer
Balance between keto (C=O) and enol (C=C–OH) forms
30
Question
What drives the enol to keto tautomerization in acidic/base conditions?
Answer
Proton transfer and stabilization of carbonyl formation