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Which molecules show an appropriate number of bonds around each carbon atom?

Select the three that apply.
View Available Hint(s)for Part A

CH3CH2CH2OH with an OH group attached to the third (from left to right) carbon.
H2NCHCOH with an O atom double-bonded to the second (from left to right) carbon.
There is a six-membered ring. An oxygen atom is double-bonded to the first and the fifth (clockwise) members. An H atom is attached to the second, the third, the fourth, and the sixth members. There is a double bond between the second and the third members. The fourth and the sixth members are N atoms, and the other members are C atoms.
H2CCHCH2 with one OH group attached to the first (from left to right) and the second carbons and an O atom double-bonded to the third carbon.
CH2CHCH3 with a double bond between the first (from left to right) and second carbons.

1 answer

To determine which molecules show an appropriate number of bonds around each carbon atom, we need to remember that carbon typically forms four bonds (single, double, or triple):

  1. CH3CH2CH2OH (propan-1-ol): The first carbon (CH3) has 4 bonds, the second carbon (CH2) has 2 bonds, the third carbon (CH2) has 2 bonds, and the carbon to which the OH group is attached also maintains 4 bonds (with the OH group counted as one bond).

    • Bonds: 1st carbon = 4, 2nd carbon = 4, 3rd carbon = 4. All carbons have an appropriate number of bonds.

  2. H2NCHCOH: The first carbon (attached to the NH2) has 3 bonds (one to the N, one to the second carbon, and one to the OH). The second carbon has 4 bonds (1 to the first carbon, 1 to the third carbon, and 1 double bond to O). The third carbon has 4 bonds (1 to the second carbon, 1 to the OH).

    • Bonds: 1st carbon = 3, 2nd carbon = 4, 3rd carbon = 4. The first carbon does not have enough bonds (only 3).

  3. Cyclic structure with N atoms: In the described six-membered structure (two N atoms and four C atoms), we need to examine each member: each carbon forms the appropriate number of bonds; C atoms with double bonds have 4 total bonds.

    • Bonds: 1st carbon = 4, 2nd carbon (with double bond) = 4, 3rd carbon = 4, 4th carbon = 4. All carbons have the right number of bonds.

  4. H2CCHCH2: The first carbon (H2C) forms 3 bonds (2 with H and 1 with the second carbon). The second carbon has 3 bonds (1 with first, 1 with OH, and 1 with the third carbon). The third carbon also forms 4 bonds (2 with OH and the two CH2).

    • Bonds: 1st carbon = 3, 2nd carbon = 4, 3rd carbon = 4. The first carbon does not have enough bonds (3).

  5. CH2CHCH3: The first carbon (with one bond to the second) has 3 bonds (1 to the second). The second carbon forms 4 bonds (2 to CH2 and 1 to CH3). The carbon forming double bond also makes 4 total bonds.

    • Bonds: 1st carbon = 3, 2nd carbon = 4, 3rd carbon = 4. The first carbon does not have enough bonds.

Therefore, the molecules that show an appropriate number of bonds are:

  1. CH3CH2CH2OH
  2. Cyclic structure with 2 N atoms
  3. H2CCHCH2 does not contribute as the first has not enough bonds.

The correct answers are molecules 1 and 3 based on counting carbon bonds accurately. The second molecule has two evident discrepancies.

So, the correct selections are:

  • CH3CH2CH2OH
  • Cyclic structure with 2 N atoms
  • CH2CHCH3

Please verify the cyclic structure form coinciding with carbon bonds.