Question

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) tetraethyl lead \(\left[\mathrm{Pb}\left(\mathrm{CH}_{2} \mathrm{CH}_{3}\right)_{4}\right],\) which is 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 \(\left[\left(\mathrm{NH}_{2}\right)_{2} \mathrm{CO}\right],\) a fertilizer; and \((\mathrm{g})\) glycine \(\left(\mathrm{NH}_{2} \mathrm{CH}_{2} \mathrm{COOH}\right),\) an amino acid.

Short answer

Each molecule has a specific Lewis structure, highlighting bonds and electron pairs.

Step-by-step solution

Understand What Lewis Structures Represent

Lewis structures are diagrams that show the bonding between atoms of a molecule, as well as the lone pairs of electrons that may exist.

Methanol (CH₃OH)

1. Count the valence electrons: C (4) + H (1x3) + O (6) + H (1) = 14 electrons. 2. Oxygen needs 2 bonds (usually making 2 single bonds) and also has two lone pairs. Hydrogen only forms 1 bond. 3. The central atom is Carbon which forms 4 single bonds: 3 with Hydrogens and 1 with Oxygen. Oxygen's other bond is with a lone Hydrogen. 4. Draw the structure: O bonded to C (in the middle) and 3 Hydrogens to C with "OH" having a single bond to another H.

Ethanol (CH₃CH₂OH)

1. Count the valence electrons: C (4x2) + H (1x6) + O (6) = 20 electrons. 2. Connect 2 carbons linearly (C-C), then bonds to Hydrogens. One carbon (CH₂) will bond to Oxygen with the typical single bond to OH (the hydroxyl group). 3. Complete the Lewis structure by connecting CH₃-C-(OH), placing hydrogens around each carbon.

Tetraethyl Lead [Pb(CH₂CH₃)₄]

1. Ethyl groups ( 2. Connect four ethyl groups to lead, each have 2 carbons which must connect as CH₂-CH₃ structures. 3. Draw using: Pb in center, and expand with (CH₂-CH₃)'s around it.

Methylamine (CH₃NH₂)

1. Count valence electrons: C (4) + N (5) + H (1x5) = 14 electrons. 2. Nitrogen forms 3 single bonds and has 1 lone pair, Carbon forms 4 single bonds. 3. Connect the CH₃ (carbon group) to Nitrogen. Place 2 hydrogens and a lone pair on nitrogen.

Mustard Gas (ClCH₂CH₂SCH₂CH₂Cl)

1. Count valence electrons: Cl (7x2) + C (4x4) + H (1x4) + S (6) = 48 electrons. 2. Draw the backbone structure: Cl—CH₂—CH₂—S—CH₂—CH₂—Cl. 3. Attach each chlorine on the end and fill in Hydrogens completing with typical C—H, C—S bonds.

Urea \\[\left(\mathrm{NH}_{2}\right)_{2} \mathrm{CO}\]

1. Count the valence electrons: N (5x2) + H (1x4) + C (4) + O (6) = 24 electrons. 2. Carbon functions centrally binding oxygens (double bond) and amine groups. 3. Visualize it: O=C (central) connects with amine groups (NH₂) in linear fashion.

Glycine (NH₂CH₂COOH)

1. Count valence electrons: N (5) + H (1x5) + C (4x2) + O (6x2) = 30 electrons. 2. Structures amines (NH₂) and carboxylic groups alter infrastructure of central links. 3. Draw NH₂ connected to CH₂, next follows COOH (carbon group with double bond to O, and OH).

Key concepts

Organic Molecules

Organic molecules are primarily composed of carbon atoms, stabilized through bonds with elements like hydrogen, oxygen, and nitrogen. These molecules form the backbone of many essential substances, including those involved in biological processes and industrial applications.
Carbon's unique ability to form four covalent bonds enables a vast array of molecular configurations. This versatility is evident in organic compounds, from simple molecules like methanol and ethanol to complex structures like proteins and DNA. Understanding their structure is crucial to comprehending their function and reactivity.
Drawing Lewis structures helps visualize these configurations. They depict how atoms are arranged and bonded in a molecule, showing both shared electrons in bonds and lone electron pairs. Using Lewis structures, one can predict the shape and properties of the molecule based on its constituent atoms and their connectivity.

• Carbon forms the skeleton of organic molecules.
• Lewis structures reveal the arrangement of atoms.
• These insights help explain molecular behavior.

Valence Electrons

Valence electrons are the outermost electrons of an atom and play a pivotal role in chemical bonding. These electrons are involved in forming bonds with other atoms, dramatically impacting a molecule's properties and reactivity.
In drawing Lewis structures, counting valence electrons correctly ensures an accurate depiction of the molecule's bonds and lone pairs. For example, carbon, typically with four valence electrons, can form up to four bonds with other atoms like hydrogen and oxygen, as seen in molecules like methanol and ethanol.
Knowing the exact number of valence electrons helps determine how many bonds an atom can form, which is essential for constructing Lewis structures accurately.

• Valence electrons dictate bonding capabilities.
• Accurate electron counting is crucial.
• This knowledge guides the formation of accurate Lewis diagrams.

Bonding Pairs

Bonding pairs are pairs of electrons shared between atoms in a molecule to form a covalent bond. These bonds create the primary structural framework in molecules, particularly organic compounds.
For instance, in a methanol molecule ( ext{CH}_3 ext{OH}), carbon shares electrons with three hydrogens and one oxygen, forming four single bonds. Similarly, in ethanol, bonding pairs connect the carbon atoms, as well as carbon with hydrogen and oxygen, creating the molecule's linear structure.
Recognizing bonding pairs in a Lewis structure highlights how electrons achieve stability through sharing, fulfilling the octet rule for most atoms involved in organic molecules.

• Bonding pairs link atoms in the molecule.
• They establish the molecular framework.
• Recognizing them helps in drawing accurate structures.

Lone Pairs

Lone pairs are pairs of valence electrons that are not shared with another atom and do not participate in bonding. However, they influence the molecule's shape and reactivity significantly.
In a molecule like methanol ( ext{CH}_3 ext{OH}), the oxygen atom has two lone pairs of electrons. These pairs impact the molecule's geometry, making the oxygen atom have a bent, rather than linear, shape. This determines the molecular properties such as polarity and intermolecular interactions like hydrogen bonding.
Lone pairs can also be found in other organic molecules like methylamine and urea, where they are often located on atoms such as nitrogen and oxygen. Identifying these lone pairs in Lewis structures helps predict possible interactions and the overall shape of the molecule.

• Lone pairs impact molecular geometry.
• They are non-bonding electron pairs.
• Recognizing them aids in understanding molecular properties.