Question

Give condensed and bond line structural formulas and identify the functional group(s) present, if any, for : (a) \(2,2,4\) -Trimethylpentane (b) 2-Hydroxy-1,2,3-propanetricarboxylic acid (c) Hexanedial

Short answer

(a) Alkane; (b) Hydroxyl and Carboxylic Acid; (c) Aldehyde groups.

Step-by-step solution

Understand the IUPAC Names

To solve this, you need to first understand what the given IUPAC names mean. The compounds are: (a) 2,2,4-Trimethylpentane, (b) 2-Hydroxy-1,2,3-propanetricarboxylic acid, (c) Hexanedial. A good first step is to break down their names into base structure and substituents.

Draw the Condensed Structural Formula for Each Compound

The condensed structural formula gives a simpler view of the molecular structure. For (a) 2,2,4-Trimethylpentane, the main chain is pentane with three methyl groups at positions 2, 2, and 4: \((CH_3)_3CCH_2CH_2CH_3\). For (b) 2-Hydroxy-1,2,3-propanetricarboxylic acid, the structure reveals a propanetricarboxylic acid backbone with a hydroxy group at position 2: \(C(OH)(COOH)(CH_2COOH)_2\). For (c) Hexanedial, it's a 6-carbon chain with an aldehyde group (\(-CHO\)) at each end: \(OHC(CH_2)_4CHO\).

Draw the Bond Line Structural Formula for Each

The bond line structural formula uses lines to represent chemical bonds. For (a), draw a straight chain with two methyl groups at the second carbon and one at the fourth: /\_\_/\_/\_. For (b), start with a linear chain for propanetri-, add \(OH\) at the second carbon and \(COOH\) groups at the first, second, and third carbons. For (c), draw a 6-carbon chain with an aldehyde group at each end: \(_\_ \_ \=O\) and \(\_\_\_ \_ \=O\).

Identify Functional Groups

Look for functional groups in each structure. In (a), there is an alkane (no functional groups). In (b), the functional groups are hydroxyl \(-OH\) and carboxyl \(-COOH\). In (c), the functional group is aldehyde \(-CHO\).

Key concepts

Condensed Structural Formula

The condensed structural formula is a compact way of representing molecules in organic chemistry. It indicates the elements present and their arrangement, offering a simplified view compared to other models. You can think of it as a shorthand notation that communicates the essential parts of a molecule without excessive detail.
To write a condensed structural formula:

• Identify the backbone, or the main chain of carbon atoms.
• Group the identical atoms together to minimize repetition.
• Specify branching points using parentheses for clarity.

For example, in the compound 2,2,4-Trimethylpentane, the main carbon chain is pentane, with additional methyl groups attached at specific positions. Thus, the condensed structural formula becomes \((CH_3)_3CCH_2CH_2CH_3\), showing clearly that there are three methyl groups attached to the second carbon.
Such formulas are extremely helpful because they enable chemists to grasp the molecule's structure quickly without having to draw it in full, promoting efficient communication and understanding.

Bond Line Structural Formula

The bond line structural formula, often referred to simply as a "line diagram," is another method to depict the structures of organic compounds. It is one of the most efficient and preferred ways in chemistry to illustrate molecular skeletons. In this format, each line junction or endpoint represents a carbon atom, with hydrogen atoms implied rather than explicitly drawn.

• Straight lines indicate bonds between carbon atoms.
• Angles or junctions of lines suggest a change in the direction of the chain and indicate carbon atoms.
• Functional groups and atoms other than carbon and hydrogen are explicitly written.

For example, consider the bond line structure of 2,2,4-Trimethylpentane. The main chain appears as a zigzag line, showing carbon connectivity, with methyl groups branching off at specified points. This diagram is especially favored because it reduces clutter, highlighting only the essential parts of the molecular structure and ignoring unnecessary hydrogen atoms.

Functional Groups

Functional groups are specific groups of atoms within molecules that have distinct properties and reactions. They are the key determining factor of a compound's reactivity and can significantly alter the physical and chemical properties of the molecule. Understanding these groups is crucial in predicting chemical behavior and interactions.

Common functional groups include:

• Hydroxyl group (-OH), as seen in alcohols, which affects solubility and boiling points.
• Carboxyl group (-COOH), seen in carboxylic acids, known for their acidity.
• Aldehyde group (-CHO), present in aldehydes, influencing the compound's reactivity with nucleophiles.

In the context of the given compounds, for instance, 2-Hydroxy-1,2,3-propanetricarboxylic acid contains both hydroxyl (-OH) and carboxyl (-COOH) groups, contributing to its acidic nature and solubility in water. Recognizing functional groups helps chemists understand how molecules might interact and react in various conditions.