Question

Draw each molecule given its name and the following information. (a) Nitroglycerin, also known as \(1,2,3\) -trinitroxypropane, the active ingredient in dynamite and a medication administered to people having a heart attack, (Hint: The nitroxy group is the conjugate base of nitric acid.) (b) Putrescine, also known as \(1,4\) -diamino-butane, the compound responsible for the odor of putre-fying fish, ( c) Cyclohexanone, the precursor to Nylon, (a) \(1,1,2,2\) -tetrafluoroethene, the precursor to Teflon, (e) Oleic acid, also known as cis-9-octanedecenoic acid, a monounsaturated fatty acid found in many fats and oils.Draw the correct isomer.

Short answer

(a) Nitroglycerin: C_3H_5(ONO_2)_3 (b) Putrescine: H_2N-(CH_2)_4-NH_2 (c) Cyclohexanone: \(\displaystyle C_{6} H_{10}{\rm{O}}\) (d) 1,1,2,2-tetrafluoroethene: \(\displaystyle C_{2}{F_{4}}\) (e) Oleic acid: \(\displaystyle CH_{3}( CH_{2})_{7} CH{=}CH( CH_{2})_{7}{\rm{COOH}}\)

Step-by-step solution

(a) Nitroglycerin, also known as 1,2,3-trinitroxypropane

: 1. Identify the functional groups: Nitroglycerin has three nitroxy groups (the conjugate base of nitric acid) attached to a propane structure. 2. Draw the propane molecule: A propane molecule has 3 carbon atoms. 3. Attach the nitroxy groups: There are 3 nitroxy groups, one at each carbon (1, 2, and 3). 4. Draw the molecule: C_3H_5(ONO_2)_3

(b) Putrescine, also known as 1,4-diaminobutane

: 1. Identify the functional groups: Putrescine has two amine groups. 2. Draw the butane molecule: A butane molecule has 4 carbon atoms. 3. Attach the amine groups: There are two amine groups, one at carbon 1 and one at carbon 4. 4. Draw the molecule: H_2N-(CH_2)_4-NH_2

(c) Cyclohexanone

: 1. Identify the functional groups: Cyclohexanone has a ketone group. 2. Draw the cyclohexane molecule: A cyclohexane molecule has 6 carbon atoms in a ring. 3. Attach the ketone group: Replace one carbon-hydrogen bond with a carbon-oxygen double bond to form the ketone group. 4. Draw the molecule: \(\displaystyle C_{6} H_{10}{\rm{O}}\)

(d) 1,1,2,2-tetrafluoroethene

: 1. Identify the functional groups: 1,1,2,2-tetrafluoroethene has four fluorine atoms and a C=C double bond. 2. Draw the ethene molecule: An ethene molecule has 2 carbon atoms and a double bond between them. 3. Attach the fluorine atoms: Replace four hydrogen atoms with fluorine (F) atoms, 2 on each carbon. 4. Draw the molecule: \(\displaystyle C_{2}{F_{4}}\)

(e) Oleic acid, also known as cis-9-octanedecenoic acid

: 1. Identify the functional groups: Oleic acid has a carboxylic acid group, a cis-alkene group, and an alkyl chain. 2. Draw the main carbon backbone: An octadecenoic acid molecule has 18 carbon atoms. 3. Attach the carboxylic acid group: Replace the first carbon's hydrogen with a carboxyl group (COOH). 4. Attach the cis-alkene group: Create a cis double bond between carbons 9 and 10. 5. Draw the molecule: \(\displaystyle CH_{3}( CH_{2})_{7} CH{=} CH( CH_{2})_{7}{\rm{COOH}}\)

Key concepts

Functional Groups

Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. They are much like the identity tags of organic compounds, telling us what reactions the molecule can participate in. Here are some of the functional groups found in the exercise:

• Nitroxy Group: Present in nitroglycerin, these groups are derived from nitric acid and involve an oxygen-nitrogen double bond. In the context of nitroglycerin, these groups are attached to a propane backbone.
• Amine Group: Found in putrescine, amines consist of a nitrogen atom bonded to hydrogen atoms. Putrescine, specifically, has two amine groups, leading it to be categorized as a diamine.
• Ketone Group: The key feature in cyclohexanone, a ketone has a carbon atom double-bonded to an oxygen, typically within or at the end of a carbon chain or ring.
• Carboxyl Group: In oleic acid, this constitutes part of the carboxylic acid group, and includes a carbon-oxygen double bond along with a hydroxyl group on the same carbon.

Understanding functional groups is essential because they largely govern the chemical behavior of molecules.

Molecule Structure

The structure of a molecule fundamentally determines its properties and function. Organic molecules are often represented in a way that reflects their 3D shape and structural features. Let's explore these aspects in the context of the exercise: - **Linear and Branched Structures:** Nitroglycerin is structured around a linear propane backbone with nitroxy groups branching off each carbon. The basic shape is essentially a straight carbon chain. - **Cyclic Structures:** Cyclohexanone exemplifies cyclic structure, where six carbon atoms are arranged in a ring. Such rings are characteristic and stable structures in organic chemistry. - **Bond Types:** Ethene, a component of 1,1,2,2-tetrafluoroethene, contains a double bond ( C=C ), which affects reactivity and stability. Double bonds are shorter and stronger than single bonds. - **Cis/Trans Isomerism:** Oleic acid contains a cis double bond, giving the molecule a kink. This influences the structure, affecting how it behaves and interacts with other molecules in systems such as fats. These structural details impact the molecule's physical properties, like boiling and melting points, and chemical properties as well.

Isomerism

Isomerism refers to the phenomenon where compounds share the same molecular formula but have different structural arrangements. This concept is crucial in understanding organic molecules, as these differences can drastically alter molecular properties and functions. - **Structural Isomers:** These isomers differ in the connectivity of their atoms. In our exercise, different molecules such as butane for putrescine and propane for nitroglycerin feature distinct branching due to the attachment of different functional groups. - **Geometric Isomers:** Specifically illustrated in oleic acid with its cis configuration, geometric isomerism involves different spatial arrangements about a double bond. Cis and trans isomers have different physical properties, such as melting points, because the orientation affects how closely molecules pack together. Recognizing isomers is fundamental in chemistry, as they often represent entirely different chemical substances despite having the same formula.

Chemical Nomenclature

Chemical nomenclature is the systematic method of naming chemical compounds. It ensures that every compound has a standard name that conveys its structure and composition. Below are some aspects of chemical nomenclature relevant to the exercise: - **Systematic IUPAC Names:** The International Union of Pure and Applied Chemistry (IUPAC) provides rules for naming. For instance, nitroglycerin is called 1,2,3-trinitroxypropane, precisely indicating three nitroxy groups on a propane chain. Similarly, putrescine's alternative name, 1,4-diaminobutane, tells us there are two amine groups on a four-carbon chain. - **Common Names:** While systematic names give detailed information, common names like nitroglycerin and putrescine are often used for simplicity and tradition. - **Prefixes and Suffixes:** Roots like "butane" or "cyclohexanone" provide core structure details, while prefixes/suffixes (like "diamine" or "ketone") give insight into functional groups. Effective use of chemical nomenclature is essential for clear and consistent communication in chemistry, allowing scientists and students to deduce molecular structure directly from the name.