Draw the structure of each aldehyde or ketone. \begin{equation}\begin{array}{l}{\text { a. hexanal }} \\ {\text { b. } 2 \text { -pentanone }} \\ {\text { c. } 2 \text { -methylbutanal }} \\ {\text { d. } 4 \text { -heptanone }}\end{array}\end{equation}

Understanding the nature of aldehydes and ketones is a fundamental concept in organic chemistry. Both belong to the carbonyl functional group category, which means they have a carbon atom double-bonded to an oxygen atom (C=O). The distinguishing factor between them is their position within a carbon chain. Aldehydes are at the chain's end, signified by the suffix '-al' in nomenclature. For example, 'hexanal' indicates an aldehyde with a six-carbon chain.

Ketones have the carbonyl group located within the carbon chain, not at the end. This is denoted by the suffix '-one' and a number indicating the position of the carbonyl group. '2-pentanone' tells us the five-carbon chain hosts the C=O group at the second carbon. These structural nuances are crucial when drawing organic structures or predicting reactivity and physical properties of these compounds in organic chemistry.

In organic chemistry, functional groups are specific groups of atoms within molecules that determine their characteristic chemical reactions. Functional groups are the reactive parts of molecules. Besides aldehydes and ketones, there are many other functional groups, such as alcohols (-OH), carboxylic acids (-COOH), amines (-NH2), and ethers (R-O-R), each defining a particular class of compounds.

Recognizing these functional groups allows chemists to deduce the physical properties, reactivity, and polarity of organic compounds. For instance, the presence of a hydroxyl (-OH) group makes a molecule an alcohol and generally increases its boiling point due to hydrogen bonding. When approaching organic synthesis or analysis, identifying functional groups is an essential skill for predicting and understanding chemical behavior.

Naming organic compounds, also known as nomenclature, follows a systematic method which provides a clear, universally-understood way of identifying chemicals. It's crucial to understand these naming rules to not only communicate effectively but also to deduce structures from names. The International Union of Pure and Applied Chemistry (IUPAC) sets the standard for these rules.

The basic steps in nomenclature involve identifying the longest carbon chain, naming substituents, and numbering the chain to give the lowest numbers to the functional groups and substituents. For example, '3-methylhexane' tells us there is a six-carbon main chain with a methyl group on the third carbon. In more complex molecules, other rules such as E/Z isomerism and priority of functional groups come into play. Understanding these rules simplifies the process of drawing structures substantially.

Skeletal, or line-angle, diagrams are a shorthand way of representing molecules in organic chemistry, widely used due to their simplicity and the ease with which they can be drawn. In these representations, carbon atoms are not shown explicitly but are assumed to be at each line's end and at any line intersection. Hydrogen atoms bonded to carbons are also not shown unless they are part of a functional group or are necessary for denoting stereochemistry.

Each line or zigzag represents a carbon-carbon bond, and the length or angle of the line has no bearing on the actual bond length or angle in the molecule—it's just for easy visualization. Functional groups like carbonyl groups (C=O) for aldehydes and ketones are shown, as they're central to understanding the molecule's properties. When you're learning to draw skeletal structures, remember that all carbon atoms must have four bonds, which helps in placing the hydrogen atoms correctly.