Question

Indicate whether each statement is true or false: (a) If you use data from Table 8.3 on bond enthalpies, you can show that the more \(\mathrm{C}-\mathrm{H}\) bonds a molecule has compared to \(\mathrm{C}-\mathrm{O}\) and \(\mathrm{O}-\mathrm{H}\) bonds, the more energy it can store. (b) Trans fats are saturated. ( c) Fatty acids are long-chain carboxylic acids. (d) Monounsaturated fatty acids have one CC single bond in the chain, while the rest are double or triple bonds.

Short answer

False (a), False (b), True (c), False (d). Statement (a) is not entirely accurate because bond enthalpies depend on the specific bonds, statement (b) is false as trans fats are unsaturated, statement (c) is true as fatty acids consist of long hydrocarbon chains with a carboxyl group, and statement (d) is false because MUFAs have only one double bond and the rest are single bonds.

Step-by-step solution

Statement (a) - Analysing Bond Enthalpies Relation with Energy Storage

To find out whether it's true that having more C-H bonds in a molecule compared to C-O and O-H bonds indicates more energy storage, we must look at the bond enthalpies of these bonds. Recall that bond enthalpy is the amount of energy required to break a particular bond, which means a higher bond enthalpy indicates more energy stored. We know that the average bond enthalpies for C-H, C-O, and O-H bonds are approximately as follows: - C-H: 413 kJ/mol - C-O: 358 kJ/mol - O-H: 467 kJ/mol From these values, we can clearly see that the C-H bond has an intermediate bond enthalpy compared to C-O and O-H bonds. But since O-H bond has a higher bond enthalpy, this can't be generalized over all cases. In some cases, C-H bonds may store more energy in the molecule compared to C-O and O-H, and in some cases, it may not. Hence, statement (a) is false.

Statement (b) - Analyzing Trans Fats Saturated Nature

Trans fats are a type of unsaturated fat. They are chemically distinct from saturated fats, which have all single bonds between their carbon atoms. Trans fats are characterized by the presence of at least one trans double bond between carbon atoms in their chains. Therefore, statement (b) is false because trans fats are not saturated fats.

Statement (c) - Describing Fatty Acids

Fatty acids are essentially long-chain carboxylic acids, which consist of a hydrocarbon chain connected to a carboxyl (COOH) functional group. These hydrocarbon chains have various lengths and may be saturated (all single bonds) or unsaturated (one or more double/triple bonds). Based on this understanding of fatty acids' structure, statement (c) is true.

Statement (d) - Describing Monounsaturated Fatty Acids

Monounsaturated fatty acids (MUFAs) have a single double bond in their hydrocarbon chains, indicating that one unsaturated site is present. The rest of the bonds in these chains are single bonds, as adding more double or triple bonds would make them polyunsaturated fatty acids (PUFAs). Hence, statement (d) is false, as it mistakenly claims that monounsaturated fatty acids have one single bond in their chains while the rest are double or triple bonds. On the contrary, MUFAs have just one double bond, with the rest being single bonds.

Key concepts

Understanding Chemical Bonds

At the heart of chemistry lies the concept of chemical bonds, which are the forces holding atoms together to form molecules and compounds. There are several types of bonds, with covalent, ionic, and metallic being the most common.

In covalent bonds, atoms share one or more pairs of electrons. An important aspect to consider is the strength of these bonds, which is described by bond enthalpy—an indicator of how much energy is required to break the bond. Generally, a higher bond enthalpy means more energy is stored within the bond. This is important when considering how molecules will interact, react, and how they store energy.

The Role of Trans Fats

Our understanding of dietary fats has evolved significantly, particularly when examining the health implications of trans fats. These are types of unsaturated fats that contain at least one trans double bond, which alters the molecule's configuration. This configuration can interfere with metabolism and is associated with negative health outcomes.

Trans fats are not saturated, which is a common misconception. Saturated fats have no double bonds, whereas trans fats' defining feature is their trans double bonds. Knowledge of such distinctions is vital in fields such as nutrition and food chemistry, where the types of fats consumed can drastically affect health.

Fatty Acids Explained

Fatty acids are essential to life, functioning as both energy sources and components of cell membranes. Structurally, they are long-chain carboxylic acids and can be classified as saturated, monounsaturated, or polyunsaturated. This classification depends on the number of double bonds in their hydrocarbon chain.

Saturated fatty acids have no double bonds, monounsaturated have one, and polyunsaturated have two or more. Being familiar with fatty acids enhances our understanding of metabolism, energy storage, and the role different fats play in our diet and health.

Monounsaturated Fatty Acids

Delving into the world of fats, it's crucial to understand monounsaturated fatty acids (MUFAs). These are fats that contain exactly one double bond in their hydrocarbon chain. The presence of this double bond changes the fat's properties and impacts its role in our diets and health.

MUFAs are typically liquid at room temperature and are considered heart-healthy dietary fats. They can be found in various foods, including olive oil and avocados. The double bond in MUFAs can influence the melting point and stability of the fatty acid, making its comprehension valuable for nutrition, food science, and health-related studies.