Question

Which of the following has all 4 types of \(C\)-atoms, i.e., \(1^{\circ}, 2^{\circ}, 3^{\circ}\) and \(4^{\circ} \mathrm{C}\)-atoms? (A) CC1(C)CCCCC1 (B) Iso-octane (C) CC1CCC2CCCCC2C1 (D) Neo-pentane

Short answer

None of the given molecules (A, B, C, and D) have all 4 types of carbon atoms (1°, 2°, 3°, and 4°).

Step-by-step solution

Identify the 4 types of carbon atoms

Before analyzing the given molecules, it's important to understand the 4 types of carbon atoms: - 1° (primary) carbon atom: bonded to only one other carbon atom. - 2° (secondary) carbon atom: bonded to two other carbon atoms. - 3° (tertiary) carbon atom: bonded to three other carbon atoms. - 4° (quaternary) carbon atom: bonded to four other carbon atoms.

Analyze molecule (A)

Molecule A: CC1(C)CCCCC1 This molecule contains a 7-membered ring with a methyl group bonded to one of the carbons in the ring. The carbons in the ring are 2°, and the methyl group's carbon is 1°. There are no 3° or 4° carbon atoms in this molecule.

Analyze molecule (B)

Molecule B: Iso-octane (2,2,4-trimethylpentane) The structure of iso-octane consists of a pentane chain, with methyl groups attached to the second and fourth carbons from one end. The carbon atoms in the main chain are 2°, except for the terminal carbons, which are 1°. The carbons in the methyl groups are also 1°. There are no 3° or 4° carbon atoms in this molecule.

Analyze molecule (C)

Molecule C: CC1CCC2CCCCC2C1 This molecule contains two fused rings: a 5-membered ring and a 6-membered ring. The carbons that are shared between the two rings are 3°. The other carbons in the rings are 2°, except for the carbons in the methyl group, which are 1°. There are no 4° carbon atoms in this molecule.

Analyze molecule (D)

Molecule D: Neo-pentane (2,2-dimethylpropane) Neo-pentane has a central carbon atom (4°) bonded to four other carbons and three peripheral carbon atoms that are bonded to one other carbon atom (1°) as methyl groups. The central carbon atom is a 4° carbon, while the other carbon atoms are 1°.

Determine the molecule with all 4 types of carbon atoms

After analyzing all the molecules, we can see that none of the given molecules have all 4 types of carbon atoms (1°, 2°, 3°, and 4°).

Key concepts

primary carbon

In organic chemistry, a primary carbon is vital in molecular structure recognition. It is characterized by being bonded to only one other carbon atom. This feature makes primary carbons the least branched in a carbon chain. You can often find them at the terminal ends of a carbon chain, where they have the flexibility for various chemical reactions.

For instance, take molecule B, iso-octane. This molecule includes primary carbons at its terminal ends as well as in its additional methyl groups. These primary carbons exhibit fewer steric hindrances due to minimal branching, allowing for reactions that primary carbons typically undergo, such as substitutions and oxidations.

secondary carbon

Secondary carbons play a pivotal role in the structure of organic compounds. These carbons are bonded to two other carbon atoms. Their position makes them key sites for certain types of reactions, especially in alcohol and alkane chemistry.

In our examples, molecule A demonstrates secondary carbons within the ring structure. Such carbons are centrally located and can often partake in reactions involving rearrangements, showcasing their importance in synthesizing more complex structures. Secondary carbons can be identified in linear chains as well as branched hydrocarbons, indicating where the molecule's flexibility in reactions lies.

tertiary carbon

Tertiary carbons are fascinating because they are bonded to three other carbon atoms. This bonding structure increases the steric bulk around the carbon, impacting how it interacts with other molecules. In chemical reactions, tertiary carbons are less likely to participate in substitutions than primary or secondary carbons but are more reactive in forming carbocations.

Molecule C includes tertiary carbons where two rings overlap. These positions are significant since they add to the molecule's stability and play a role in maintaining its three-dimensional structure. Due to their unique bonding, tertiary carbons also play a crucial part in organic syntheses and stability analyses.

quaternary carbon

Quaternary carbons are unique as they are bonded to four other carbon atoms, featuring no hydrogen atoms directly attached to them. This makes them the most branched and offers significant rigidity and stability to a molecule’s structure.

Molecule D, neo-pentane, is a classic example of a molecule containing a quaternary carbon at its center. This four-way junction provides stability but limits reactivity. The lack of hydrogen atoms makes it unlikely for these carbons to engage in common hydrogen-related reactions, such as hydrations or oxidations. These carbon atoms, however, contribute to the strong structural framework of many complex organic compounds.