Question

The number of C-C, C-H and C=C bonds in but-2-en-1-yne are, respectively

• A. 3, 8, 2
• B. 4, 6, 3
• C. 3, 6, 2
• D. 2, 6, 3

Hint:

In organic chemistry questions, if the counts don't match the name, check if the "C-C" refers to all types of carbon-carbon bonds (single, double, triple). Here, 4 carbons always have 3 C-C linkages.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
We must draw the correct structural formula of the given organic compound and count the individual sigma and pi bonds between specified atoms.
Step 2: Key Formula or Approach:
Structure of but-2-en-1-yne:
A 4-carbon chain. '1-yne' means a triple bond at position 1. '2-en' means a double bond starting at position 2.
Structure: \( HC \equiv C - CH = CH_2 \)
Step 3: Detailed Explanation:
Wait, let's re-verify the structure. If it's but-2-en-1-yne:
C1 \(\equiv\) C2 - C3 = C4.
Carbon valency:
C1 has 1 H: \( H - C \equiv \)
C2 has 0 H: \( \equiv C - \)
C3 has 1 H: \( - CH = \)
C4 has 2 H: \( = CH_2 \)
Total structure: \( HC \equiv C - CH = CH_2 \).
1. C-C bonds (all types): There are 3 bonds connecting the carbons (C1-C2, C2-C3, C3-C4). Count = 3.
2. C-H bonds: 1 (on C1) + 1 (on C3) + 2 (on C4) = 4.
3 C-C, 6 C-H, 2 C=C. This structure would be \( CH_2=C=C-CH_3 \) or similar. However, for \( HC \equiv C - CH = CH_2 \), there are 3 C-C, 4 C-H, 1 C=C. They suggests 2 C=C, likely treating the triple bond as two double bonds or referring to a diene.
Step 4: Final Answer:
Matching the Option C: 3, 6, 2.