Question

Draw a compound that: (a) Has only primary and tertiary carbons (b) Has no secondary or tertiary carbons (c) Has four secondary carbons

Short answer

(a) 2,2,3,3-tetramethylbutane; (b) Tetramethylmethane; (c) Cyclobutane.

Step-by-step solution

Understanding Carbon Classifications

Carbons in organic chemistry are classified based on the number of carbon atoms they are attached to. A primary carbon (1°) is attached to only one other carbon, a secondary carbon (2°) to two, a tertiary carbon (3°) to three, and a quaternary carbon (4°) to four other carbons.

Analyzing Part (a)

We need a compound that contains only primary and tertiary carbons. A possible structure is 2,2,3,3-tetramethylbutane. This compound has primary carbons at the ends and tertiary carbons where the methyl groups are attached.

Analyzing Part (b)

For this part, we require a compound that has no secondary or tertiary carbons. Only primary and quaternary carbons should be present. Tetramethylmethane (commonly known as neopentane) fits this requirement, as it is composed of a central quaternary carbon surrounded by four primary carbons.

Analyzing Part (c)

In this scenario, we need a compound with four secondary carbons. Cyclobutane fits this requirement, as it consists of a four-carbon ring structure where each carbon is bonded to two other carbons, making them all secondary.

Key concepts

Primary Carbon

A primary carbon atom is a simple character in the world of organic chemistry. It is defined by its connectivity to only one other carbon atom. This type of carbon is often found at the ends of a carbon chain, forming the terminal links in a molecular structure. Key aspects of primary carbons include:

• They are connected to one carbon atom and three hydrogen atoms, generally speaking.
• In molecular diagrams and structural formulas, they are typically at the chain's edge.
• They play a crucial role in influencing the physical properties of molecules like boiling and melting points due to their location in the structure.

Understanding primary carbons helps in visualizing and constructing molecular structures, an essential skill in organic chemistry.

Secondary Carbon

A secondary carbon atom is one that is linked to two other carbon atoms in a molecule. They often form part of the carbon backbone in organic compounds. Secondary carbons are not found at the extremities of linear chains but within the chain themselves. Characteristics of secondary carbons include:

• They typically have a bond with two carbon atoms and are commonly bonded to two hydrogen atoms.
• In linear or ringed carbon structures, these carbons create branching points, contributing to the molecule's shape and reactivity.
• They are central to many common organic compounds, like alkanes and alcohols, and determine many of these compounds' behaviors.

Recognizing secondary carbons helps students understand how molecular structures impact chemical properties.

Tertiary Carbon

Tertiary carbon atoms serve as key points in organic molecules where three carbon atoms connect. These are highly important in branching and can significantly influence a molecule's shape and properties. Insightful aspects of tertiary carbons include:

• They are attached to three other carbon atoms, often with one hydrogen atom.
• Such carbons are found in the interior of a molecule and contribute to branching, which can alter a molecule's reactivity and stability.
• Examples of molecules containing tertiary carbons, such as 2,2,3,3-tetramethylbutane, show their importance in increasing the complexity and three-dimensional shape of structures.

Understanding the concept of tertiary carbons allows chemists to manipulate and predict molecular interactions better.

Quaternary Carbon

Quaternary carbons are unique because they bond with four other carbon atoms. These carbons are at the heart of compact, highly branched molecules, giving these compounds distinctive characteristics. Key traits of quaternary carbons include:

• They are fully substituted, without any hydrogen atoms attached.
• Found in highly branched hydrocarbons, like tetramethylmethane (neopentane), these carbons provide a central anchor point for the structure.
• The presence of quaternary carbons often influences the compound's boiling and melting points and makes the substance generally more stable.

Grasping the role of quaternary carbons is essential for understanding complex molecular structures and for applications in synthetic chemistry.