Problem 8 - Chemistry and Chemical Reactivity

Question

Draw a Lewis structure for each of the following molecules: (a) methanol, \(\mathrm{CH}_{3} \mathrm{OH}\) (b) vinyl chloride, \(\mathrm{H}_{2} \mathrm{C}=\mathrm{CHCl}\), the molecule from which PVC plastics are made (c) acrylonitrile, \(\mathrm{H}_{2} \mathrm{C}=\mathrm{CHCN}\), the molecule from which materials such as Orlon are made EQUATION CANT COPY

Step-by-Step Solution

Answer

Draw Lewis structures showing all atoms bonded with lines and fill octets with dots for lone pairs.

Step 1: Understand the Components of Methanol

Methanol has the chemical formula \( \mathrm{CH}_{3}\mathrm{OH} \). It consists of one carbon (C) atom, four hydrogen (H) atoms, and one oxygen (O) atom. Carbon is the central atom and forms four bonds: three with hydrogen atoms and one with an oxygen atom.

Step 2: Draw the Lewis Structure for Methanol

- Begin with the central carbon atom.- Draw single bonds by connecting carbon to the three hydrogen atoms: \( \mathrm{H}-\mathrm{C}-\mathrm{H} \).- Connect the remaining hydrogen and the oxygen atom to the carbon using another bond: \( \mathrm{H}-\mathrm{C}-(\mathrm{H})_{2}-\mathrm{O}-\mathrm{H} \).- Place dots around the oxygen to complete its octet (4 extra electrons forming two pairs).

Step 3: Understand the Components of Vinyl Chloride

Vinyl chloride has the formula \( \mathrm{H}_{2}\mathrm{C}=\mathrm{CHCl} \). There are three central atoms: two carbon atoms connected by a double bond, and one carbon is attached to two hydrogens while the other is attached to one hydrogen and one chlorine.

Step 4: Draw the Lewis Structure for Vinyl Chloride

- Start with two carbon atoms and draw a double bond between them: \( \mathrm{C} = \mathrm{C} \).- Attach two hydrogen atoms to one of the carbon atoms: \( \mathrm{H}_{2}\mathrm{C}= \).- Attach one hydrogen and one chlorine atom to the second carbon: \( \mathrm{CHCl} \).- Draw dots around chlorine to complete its octet (3 lone pairs).

Step 5: Understand the Components of Acrylonitrile

Acrylonitrile is represented by \( \mathrm{H}_{2}\mathrm{C}=\mathrm{CHCN} \). It includes two double bonded carbon atoms, and the second carbon is also triple bonded to a nitrogen atom from another cyanide molecule (\( \mathrm{CN} \)). The first carbon is connected to two hydrogens.

Step 6: Draw the Lewis Structure for Acrylonitrile

- Begin with two carbon atoms linked by a double bond: \( \mathrm{C} = \mathrm{C} \).- Attach two hydrogen atoms to the first carbon: \( \mathrm{H}_{2}\mathrm{C}= \).- Attach a cyanide group (\( \mathrm{C} \equiv \mathrm{N} \)) to the second carbon: \( (\mathrm{CH} \equiv \mathrm{CN}) \).- Draw dots to fill the nitrogen's octet and its remaining lone pair (2 pairs on nitrogen).

Key Concepts

Methanol

Methanol, also known as wood alcohol, is an organic compound with the formula \( \mathrm{CH}_{3} \mathrm{OH} \). It is one of the simplest alcohols and consists of four hydrogen atoms, one carbon atom, and one oxygen atom. The Lewis structure of methanol is essential for understanding its chemical properties and reactivity. To draw the Lewis structure:

• Begin with the central carbon atom, because carbon can form four covalent bonds.
• Attach three hydrogen atoms to the carbon, forming single bonds with each: \( \mathrm{H}-\mathrm{C}-\mathrm{H} \).
• Connect the oxygen atom to the remaining carbon bond.
• Finally, connect a hydrogen atom to the oxygen to complete the structure: \( \mathrm{H}-\mathrm{C}-(\mathrm{H})_{2}-\mathrm{O}-\mathrm{H} \).
• Oxygen needs two extra lone pairs to complete its octet, so place four dots around it.

Methanol's Lewis structure shows that it has four single covalent bonds. This structure allows it to be highly polar and enables it to dissolve in water and form hydrogen bonds with other molecules.

Vinyl Chloride

Vinyl chloride is a key industrial chemical used in the production of polyvinyl chloride (PVC) plastics. Its chemical formula is \( \mathrm{H}_{2} \mathrm{C}=\mathrm{CHCl} \). In the Lewis structure of vinyl chloride, the arrangement of atoms highlights the presence of different functional groups:

• Start by identifying the central components: two carbon atoms connected by a double bond \( \mathrm{C} = \mathrm{C} \).
• The first carbon atom is bonded to two hydrogen atoms \( \mathrm{H}_{2}\mathrm{C}= \).
• The second carbon atom connects to one hydrogen and a chlorine atom \( \mathrm{CHCl} \).
• Chlorine requires three lone pairs to satisfy its octet; thus, place six dots around it.

The double bond between the carbon atoms creates a planar structure, affecting vinyl chloride's physical properties and making it chemically reactive. The presence of chlorine introduces a polar character to the molecule, influencing its interactions with other substances.

Acrylonitrile

Acrylonitrile is an important compound used in the manufacture of synthetic fibers like Orlon. Its formula is \( \mathrm{H}_{2} \mathrm{C}=\mathrm{CHCN} \). To understand its Lewis structure, focus on the arrangement of bonds among carbon, hydrogen, and the cyanide group:

• Start with two carbon atoms forming a double bond \( \mathrm{C} = \mathrm{C} \).
• The first carbon atom is bonded to two hydrogen atoms \( \mathrm{H}_{2}\mathrm{C}= \).
• The second carbon is connected to the cyanide group \( \mathrm{C} \equiv \mathrm{N} \), involving a triple bond with nitrogen.
• Nitrogen, like oxygen and chlorine, completes its octet with its own lone pairs; add four dots around the nitrogen atom.

The structure of acrylonitrile, with its sp hybridized carbon triple bonded to nitrogen, attributes to its linear shape and contributes to its stability and reactivity. The unique arrangement allows acrylonitrile to polymerize easily, a critical quality for forming durable and strong polymeric materials.