Draw the complete Lewis structures for the following condensed structural formulas

Draw the complete Lewis structures for the following condensed structural formulas.

a. CH3(CH2)3CH(CH3)2

b. CH3CH2COCN

c. (CH3)3CCOCHCH2

d. (CH3CH2)2CO

e. (CH3)2CHCH2Cl

The correct answer and explanation is :

Sure! Let’s first interpret each condensed formula, then draw the complete Lewis structures, and finally provide an explanation of how to do so.

a. CH3(CH2)3CH(CH3)2

Step 1: Interpret the formula

• CH3: methyl group at one end
• (CH2)3: three methylene groups in a chain
• CH(CH3)2: a carbon attached to two methyl groups (isopropyl group)

This is a branched alkane: pentane backbone with a branching at the 4th carbon.

Lewis structure:

• Carbon chain: C1 (CH3)–C2 (CH2)–C3 (CH2)–C4 (C with two CH3 branches)–C5 (CH3)

Drawing:

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

In the Lewis structure, each carbon must have 4 bonds; hydrogens fill remaining valences.

b. CH3CH2COCN

Interpretation:

• CH3CH2: ethyl group
• CO: carbonyl (C=O)
• CN: nitrile group (C≡N triple bond)

This is an acyl cyanide (ethanoyl cyanide).

Lewis structure:

• CH3–CH2–C(=O)–C≡N

Draw as:

H   H   O   N
|   |   ||  ≡
H-C-C-C-C
    |       |
    H       N

Carbonyl carbon double bonded to oxygen and single bonded to the cyanide carbon, which triple bonds to nitrogen.

c. (CH3)3CCOCHCH2

Interpretation:

• (CH3)3C: tert-butyl group
• CO: carbonyl group (C=O)
• CHCH2: vinyl group (alkene, C=C with hydrogens)

Likely tert-butyl ketone attached to a vinyl group.

Lewis structure:

• (CH3)3C–C(=O)–CH=CH2

Draw as:

       H
       |
H3C—C—C=O
  |    |
 H3C   CH=CH2
  |
 H3C

The central carbon has three methyls, connected to a carbonyl carbon, which is double bonded to oxygen and single bonded to a vinyl group.

d. (CH3CH2)2CO

Interpretation:

• (CH3CH2)2: two ethyl groups
• CO: carbonyl group (C=O)

This is diethyl ketone, or 3-pentanone.

Lewis structure:

• CH3CH2–C(=O)–CH2CH3

Draw:

H   H       O
|   |       ||
H-C-C-C-C-C-H
    |       |
    H       H

Central carbonyl carbon double bonded to oxygen and single bonded to two ethyl groups.

e. (CH3)2CHCH2Cl

Interpretation:

• (CH3)2CH: isopropyl group
• CH2Cl: chloromethyl group

This is isopropylmethyl chloride.

Lewis structure:

• (CH3)2CH–CH2–Cl

Draw as:

     H
     |
H—C—C—C—Cl
 |  |  |
 H  H  H

Central carbon bonded to two methyls and a CH2 group, which bonds to chlorine.

Explanation of Lewis Structures (approx. 300 words)

Lewis structures depict the arrangement of atoms, bonds, and lone pairs in molecules. To draw them from condensed formulas:

1. Identify the atoms and connectivity: Condensed formulas give a shorthand for bonding. Parentheses denote groups of atoms bonded together, and subscript numbers indicate repetition.
2. Determine the backbone: In organic molecules, the carbon chain is the backbone. For example, CH3(CH2)3CH(CH3)2 indicates a chain of carbons with methyl branching.
3. Assign bonds: Single bonds are between atoms written sequentially. Double or triple bonds are indicated by specific groups (CO = C=O, CN = C≡N).
4. Complete valence: Carbon forms four bonds, nitrogen three, oxygen two, and hydrogen one. Add hydrogens to fulfill valence rules where bonds are missing.
5. Account for special groups: Functional groups like carbonyls (C=O) and nitriles (C≡N) have characteristic bonding patterns.
6. Verify formal charges: In neutral organic molecules, all atoms should have zero formal charge; if not, adjust accordingly.

By following these steps, the condensed formulas can be expanded into full Lewis structures that clarify bonding and molecular geometry. For example, the formula CH3CH2COCN shows an acyl cyanide with a carbonyl and nitrile group, helping to understand the molecule’s reactivity and properties.