Question

Consider the reaction of propane with chlorine (and appropriate catalyst). a. How many different monochloro products are possible? Name them. b. How many different dichloro products are possible? Name them.

Short answer

a. Two different monochloro products are possible: 1-chloropropane and 2-chloropropane. b. Three different dichloro products are possible: 1,1-dichloropropane, 1,2-dichloropropane, and 1,3-dichloropropane.

Step-by-step solution

Draw the structure of propane

: First, draw the structure of propane, which is C3H8. Propane has three carbon atoms, with two end carbons bound to three hydrogen atoms each and the middle carbon bound to two hydrogens.

Identify the possible monochloro products

: Now replace one hydrogen atom with a chlorine atom in the propane structure. There are two possible monochloro products: one with the chlorine atom bound to an end carbon and another with the chlorine atom bound to the middle carbon. The monochloro products have the molecular formula C3H7Cl.

Name the monochloro products

: The monochloro products can be named using the IUPAC nomenclature: 1. 1-chloropropane (where the chlorine atom is bound to the first carbon) 2. 2-chloropropane (where the chlorine atom is bound to the second carbon) So, there are two different monochloro products: 1-chloropropane and 2-chloropropane.

Identify the possible dichloro products

: Next, replace two different hydrogen atoms with chlorine atoms in the propane structure. There are three possible dichloro products: two with chlorine atoms bound to the same carbon, and one with chlorine atoms bound to different carbons. These dichloro products have a molecular formula of C3H6Cl2.

Name the dichloro products

: The dichloro products can be named using the IUPAC nomenclature: 1. 1,1-dichloropropane (both chlorine atoms are on the first carbon) 2. 1,2-dichloropropane (one chlorine atom is on the first carbon, and the other is on the second carbon) 3. 1,3-dichloropropane (one chlorine atom is on the first carbon, and the other is on the third carbon) So, there are three different dichloro products: 1,1-dichloropropane, 1,2-dichloropropane, and 1,3-dichloropropane. In summary: a. There are two different monochloro products: 1-chloropropane and 2-chloropropane. b. There are three different dichloro products: 1,1-dichloropropane, 1,2-dichloropropane, and 1,3-dichloropropane.

Key concepts

Propane

Propane is a simple yet important molecule in organic chemistry. It is composed of three carbon atoms and eight hydrogen atoms, represented by the molecular formula \(C_3H_8\). Propane is part of the alkane family, characterized by single bonds between carbon atoms.

The structure of propane consists of a straight chain, with each carbon atom following a specific bonding pattern. The two end carbon atoms each bond with three hydrogen atoms, while the middle carbon bonds with two hydrogen atoms. This consistent pattern makes alkanes like propane saturated hydrocarbons.

Understanding propane's structure is crucial, especially when predicting reactions through mechanisms like chlorination.

Chlorination

Chlorination is a chemical reaction that involves adding chlorine to a compound. In the case of propane, this is typically done in the presence of UV light or heat, which act as catalysts.

During chlorination of propane, hydrogen atoms are replaced by chlorine atoms. This process happens due to free radical substitution, where a hydrogen atom is swapped out for a chlorine atom. The ability to manipulate this property makes propane a versatile molecule in synthetic organic chemistry.

In practical terms, chlorination can be controlled to produce either monochloro or dichloro products, depending on how many hydrogen atoms are replaced. This specificity is a powerful tool in creating tailored chemical products.

IUPAC Nomenclature

IUPAC nomenclature is the systematic and standard method of naming chemical compounds. It helps ensure that names are descriptive and uniform across scientific disciplines.

When it comes to naming chlorinated propane derivatives, follow these steps:

• Identify the longest carbon chain as the parent compound.
• Number the carbon atoms in a way that gives substituents the lowest possible numbers.
• Name the substituents as prefixes, including positions on the carbon chain.

For example, if a chlorine atom is attached to the first carbon, it is termed "1-chloropropane." This system ensures clarity and avoids confusion, especially important in complex organic reactions.

Monochloro products

Monochloro products are compounds that form when one hydrogen atom in propane is replaced by a chlorine atom. There are two possible monochloro propane products:

• 1-chloropropane, where the chlorine atom is on the first carbon.
• 2-chloropropane, where the chlorine atom is on the second carbon.

These products differ only in the position of the chlorine atom, a concept known as structural isomerism. Understanding these variations is essential for recognizing how slight changes in structure can affect a compound's properties and reactivity.

Dichloro products

Dichloro products result when two hydrogen atoms in propane are substituted with chlorine atoms. There are three distinct possibilities based on which hydrogens are replaced:

• 1,1-dichloropropane: both chlorines on the first carbon.
• 1,2-dichloropropane: one chlorine on the first carbon, the other on the second.
• 1,3-dichloropropane: one chlorine on the first carbon, the other on the third.

These variations demonstrate how molecular structures can greatly vary, even with the same empirical formula. Identifying these types of structural differences is crucial for mastering more advanced organic chemistry topics.