Problem 1 - Chemistry and Chemical Reactivity

Question

What is the name of the straight (unbranched) chain alkane with the formula \(\mathrm{C}_{7} \mathrm{H}_{16} ?\)

Step-by-Step Solution

Answer

Heptane

Step 1: Understand the Formula

The molecular formula given is \(\mathrm{C}_{7}\mathrm{H}_{16}\), which indicates that the compound is an alkane. Alkanes have a general formula of \(\mathrm{C}_n\mathrm{H}_{2n+2}\). This compound follows the formula for alkanes since \(2(7) + 2 = 16\).

Step 2: Determine the Number of Carbons

The formula \(\mathrm{C}_{7}\mathrm{H}_{16}\) means there are 7 carbon atoms. Alkanes are named based on the number of carbon atoms in the longest chain.

Step 3: Name the Alkane

For an alkane with 7 carbon atoms, the prefix 'hept-' is used. The name of a straight-chain alkane ends with '-ane', so the name of \(\mathrm{C}_{7}\mathrm{H}_{16}\) is heptane.

Key Concepts

Straight Chain Alkane

A straight chain alkane is an organic compound composed of only carbon and hydrogen atoms, arranged in a continuous, linear chain. This unbranched formation differentiates them from branched alkanes, which have carbon chains that fork into other branches. The simplicity of straight chain alkanes makes them ideal for studying basic hydrocarbon structures and chemical properties. Each carbon atom in a straight chain alkane bonds to the neighboring carbon atoms and enough hydrogen atoms to complete its four bonds. This consistent arrangement leads to a predictable pattern, which is an essential concept in organic chemistry.

Molecular Formula

The molecular formula of a compound provides the exact number of each type of atom present in the molecule. For example, in the formula \(\mathrm{C}_7\mathrm{H}_{16}\), there are seven carbon atoms and sixteen hydrogen atoms in the molecule.

• The molecular formula doesn't specify the arrangement of the atoms, just the quantity.
• It's crucial for determining the substance's characteristics and potential chemical reactions it can undergo.

The ability to read and understand molecular formulas is foundational for recognizing different organic compounds, like alkanes, helping to predict their physical and chemical behaviors.

Alkane General Formula

Understanding the general formula for alkanes helps predict the structure of these compounds. The general formula is \(\mathrm{C}_n\mathrm{H}_{2n+2}\), where \(n\) is the number of carbon atoms in the molecule.

• This formula exemplifies the standard pattern found in stable alkanes.
• For instance, given a compound with seven carbon atoms, like \(\mathrm{C}_7\mathrm{H}_{16}\), you would calculate the hydrogen count using \(2(7) + 2 = 16\).

Recognizing the formula enables chemists to identify and categorize alkanes correctly, ensuring that they follow the specific rules defining these hydrocarbons.

Carbon Chain Length

The length of the carbon chain in an alkane affects its physical and chemical properties and determines its nomenclature. Each length correlates with a specific prefix:

• 1 carbon: Meth-
• 2 carbons: Eth-
• 3 carbons: Prop-
• 4 carbons: But-
• 5 carbons: Pent-
• 6 carbons: Hex-
• 7 carbons: Hept-

Hence, a chain containing seven carbons uses the prefix 'hept-', making \(\mathrm{C}_7\mathrm{H}_{16}\) heptane. The longer the carbon chain, the higher the boiling and melting points, impacting how these compounds are used in real-world applications, such as fuels or solvents.