Draw Lewis structures for the following organic molecules: (a) methanol \(\left(\mathrm{CH}_{3} \mathrm{OH}\right) ;\) (b) ethanol \(\left(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}\right) ;\) (c) tetraethyllead \(\left[\mathrm{Pb}\left(\mathrm{CH}_{2} \mathrm{CH}_{3}\right)_{4}\right]\) which was used in "leaded gasoline"; (d) methylamine \(\left(\mathrm{CH}_{3} \mathrm{NH}_{2}\right),\) which is used in tanning; (e) mustard gas \(\left(\mathrm{ClCH}_{2} \mathrm{CH}_{2} \mathrm{SCH}_{2} \mathrm{CH}_{2} \mathrm{Cl}\right),\) a poisonous gas used in World War I; (f) urea [(NH \(_{2}\) ) \(_{2}\) CO], a fertilizer; and (g) glycine \(\left(\mathrm{NH}_{2} \mathrm{CH}_{2} \mathrm{COOH}\right)\), an amino acid.

Understanding the Lewis structure of methanol, or CH₃OH, starts by recognizing that methanol is a simple alcohol with three elements: carbon (C), hydrogen (H), and oxygen (O). Each element has a specific number of valence electrons: carbon has 4, hydrogen has 1, and oxygen has 6.

In the Lewis structure, we see that the carbon atom is the central figure, bonding with three hydrogen atoms and one oxygen atom. The oxygen atom also bonds with one hydrogen atom, forming the hydroxyl group (-OH) characteristic of alcohols. It's important to note that the oxygen atom also has two lone pairs of electrons, which aren’t shared with other atoms. These pairs illustrate oxygen's higher electronegativity and its tendency to keep some electrons to itself.

Ethanol (CH₃CH₂OH) is another common organic molecule, slightly more complex than methanol due to an additional carbon atom. In ethanol's Lewis structure, we build upon the same basic principles as methanol.

Each carbon atom still possesses four valence electrons, and they connect the carbon atoms to each other. The first carbon attaches to three hydrogen atoms, while the second carbon binds to two hydrogen atoms and the hydroxyl group (-OH). Like in methanol, the oxygen has two unshared pairs of electrons. The understanding of ethanol's structure is crucial for learners because it exemplifies the structures of more complex organic molecules, especially other primary alcohols.

Tetraethyllead is a more complex organic molecule, historically used as an anti-knock agent in leaded gasoline. Its chemical formula is Pb(C₂H₅)₄. The central atom in this structure is a lead (Pb) atom, surrounded by four ethyl groups (C₂H₅).

To draw its Lewis structure, you begin by putting the Pb atom at the center, showing its valence electrons ready to form bonds. Then, you add the four ethyl groups, each composed of a two-carbon chain. The first carbon in each chain bonds to the Pb atom and also connects to two hydrogen atoms, while the second carbon bonds to three hydrogen atoms. This molecule is an example of organometallic chemistry, combining metals with carbon-containing groups, a topic rich with applications and study in organic chemistry.

In organic chemistry, Lewis structures form the backbone of understanding molecular geometry and reactivity.

They allow us to predict how atoms are bonded together in a molecule and what the distribution of electrons looks like. Through Lewis structures, students learn how to distribute valence electrons, form bonds, and recognize lone pairs. Mastery of drawing these structures is essential for predicting the physical properties and reactivity of organic compounds. It's also the first step in moving towards more advanced models of molecular structure, such as molecular orbital theory or 3D VSEPR models. All these skills are foundational for anyone aiming to have a deeper comprehension of organic chemistry and its many applications in fields like medicinal chemistry and materials science.