Question

convert the condensed formula hccch(ch₃)₂ into its expanded structure. be sure to draw all hydrogen atoms. draw the expanded structure.

Explanation:

1. First, identify the carbon chain: the condensed formula $HC≡CCH(CH_3)_2$ has a 3-carbon parent chain with a triple bond between C1 and C2, and a methyl substituent on C3.
2. Add hydrogen atoms to satisfy carbon's octet rule:

• C1 (terminal, part of triple bond): bonds to 1 H.
• C2 (part of triple bond): no additional H atoms.
• C3 (bonded to C2, two methyl groups): no additional H atoms.
• Each methyl ($CH_3$) group on C3 bonds to 3 H atoms.

Answer:

The expanded structure is:

      H
      |
H-C≡C-C-CH₃
        |
        CH₃

Or written with all explicit hydrogens:
$H-C≡C-C(CH_3)(CH_3)$ with each $CH_3$ showing:

      H
      |
H-C≡C-C-H
     / \
    H   H
   /     \
  H       H

(Visually, this is a terminal hydrogen bonded to the first carbon, a triple bond between the first and second carbon, the second carbon bonded only to the first and third carbon, the third carbon bonded to the second carbon and two separate methyl groups, each methyl group having three hydrogen atoms bonded to its central carbon.)