select the best description of the molecule shown below.

Title: “Identifying Molecules: A Guide to Analyzing Chemical Structures in Education”

Answer: “Identifying Chemical Structures: How to Select the Best Description of a Molecule”


MDMA molecule

Molecules are the basic building blocks of all matter. Every substance, including the air we breathe, the food we eat, and the medicines we take are made up of molecules. Understanding the structure of molecules is essential to understanding their properties and functions.

In this article, we will focus on understanding the structure of one particular molecule. We will go through the process of selecting the best description of the molecule shown in the image above and see why it is important to get the correct description.

The molecule in the image is 3,4-methylenedioxymethamphetamine, commonly known as MDMA or “ecstasy”. It is a psychoactive drug that is widely used for its euphoric effects.

Understanding the molecular structure of MDMA is important for several reasons. Firstly, knowing the structure of a molecule helps us to understand how it interacts with other molecules. This is particularly important for drugs like MDMA, which bind to specific receptors in the brain and produce their effects through chemical interactions.

Secondly, understanding the structure of a molecule can help us to predict how it will behave under different conditions. For example, knowing the structure of MDMA can help us to predict how it will dissolve in water or how it will react with other chemicals.

Finally, understanding the structure of a molecule is important for the development of new drugs. By understanding how different molecules interact with each other, scientists can design new drugs that target specific receptors or enzymes in the body. This can lead to the development of more effective treatments for diseases.

The Molecule Shown Below


The molecule shown in the given diagram is an amino acid called glycine. This molecule is the simplest amino acid and has a chemical formula of NH2CH2COOH. It consists of a central carbon atom (denoted by C), which is attached to an amino group (NH2), a carboxyl group (COOH), a hydrogen atom (H) and a side chain (R group) that contains just a single hydrogen atom. The nitrogen atom in the amino group is connected to the central carbon atom by a single bond, while the carbon atom in the carboxyl group forms a double bond with one of the oxygen atoms.

Glycine is an important molecule in biochemistry because it is one of the building blocks of proteins. Proteins are large, complex molecules that are essential for a wide range of biological processes, including cellular signaling, transport, and defense. A protein is made up of a linear chain of amino acids that are linked together by peptide bonds. The sequence and arrangement of amino acids in a protein determine its unique three-dimensional structure and function.

One of the notable features of glycine is its small size and flexibility. The side chain of glycine is just a single hydrogen atom, which means that it can fit into tight spaces in a protein structure. This property makes glycine an important component of collagen, the most abundant protein in the human body. Collagen is a fibrous protein that provides structural support to tissues such as skin, bones, and cartilage. Glycine comprises one-third of the amino acids in collagen.

Glycine also plays a role in the nervous system as an inhibitory neurotransmitter. In this context, glycine acts as a receptor that regulates the activity of certain neurons, particularly in the spinal cord and brainstem. Dysfunction of the glycine receptor has been associated with neurological disorders such as hyperekplexia, a rare inherited disorder characterized by exaggerated startle responses.

In conclusion, glycine is a small, flexible amino acid that serves as a building block for proteins and a neurotransmitter in the nervous system. Its simple structure and unique properties make it a versatile molecule with important biological roles.

Descriptive Terms

linear molecule

Molecules are made up of atoms that are bonded together. The way in which these atoms are bonded determines the shape or structure of the molecule. The structure of a molecule plays a vital role in its physical and chemical properties. There are various descriptive terms used to determine the molecular structure of a given compound. These descriptive terms include linear, branched, cyclic and aromatic.


linear structure

A linear molecule is a straight-chain molecule. In a linear molecule, the atoms are arranged in a straight line. In other words, a linear molecule has a single, continuous line of atoms. A simple example of a linear molecule is the carbon dioxide (CO2) molecule. The carbon atom is bonded to two oxygen atoms in a straight line. Another example of a linear molecule is hydrogen cyanide (HCN). The hydrogen atom is bonded to the carbon atom, which is bonded to the nitrogen atom in a straight line.


branched structure

A branched molecule is a molecule that has one or more branches in its structure. In other words, a branched molecule is a molecule that has one or more carbon atoms with three or more bonds. These carbon atoms form branches in the molecule. An example of a branched molecule is isopentane (C5H12). Isopentane has four carbon atoms in its main chain with a branch at the second carbon atom.


cyclic structure

Cyclic molecules are molecules that have a closed-loop of atoms in their structure. In other words, the molecule forms a ring. Cyclic molecules can be either aromatic or non-aromatic. In an aromatic cyclic molecule, the ring is composed of alternating double and single bonds. Benzene is an example of an aromatic cyclic molecule. In a non-aromatic cyclic molecule, the ring is composed of only single bonds. Cyclohexane is an example of a non-aromatic cyclic molecule.


aromatic structure

Aromatic molecules are cyclic molecules that have a special kind of stability due to the presence of a delocalized ring of electrons. Aromatic compounds have a unique structure that consists of multiple benzene rings. The benzene ring is a six-membered ring with alternating double bonds. Aromatic compounds are known for their characteristic odor and many of them are used in the fragrance and flavor industry as well as in pharmaceuticals.

In conclusion, molecular structure plays a vital role in determining the physical and chemical properties of any given compound. The structure of a molecule is determined by the way in which its atoms are bonded together. The various descriptive terms used in reference to molecular structures such as linear, branched, cyclic, and aromatic help us to understand and categorize different types of molecules based on their structure and properties.

Identifying the Molecule

Molecule diagram

The molecule shown in the diagram above is an amino acid called leucine. It is an organic compound with the molecular formula C6H13NO2 and is classified as a non-polar, aliphatic amino acid.

The Structure of Leucine

Leucine structure

Leucine belongs to the group of 20 genetically encoded amino acids that make up proteins in living organisms. It is an α-amino acid that has a carboxyl group (COOH) at one end and an amino group (NH2) at the other end. In between these functional groups, there is a three-carbon chain known as the ‘propyl’ group (CH2CH(CH3)2) that gives leucine its distinctive structure.

The propyl group has a branched structure, with two methyl groups (CH3) attached to the second carbon atom of the chain. This makes leucine an isomer of several other amino acids, such as isoleucine and valine, which have similar structural features. However, the positioning of the methyl groups in leucine is different from these other amino acids, giving it unique chemical and biological properties.

The Properties of Leucine

Leucine properties

Leucine is a non-polar amino acid, meaning it is hydrophobic and not soluble in water. It has a relatively high molecular weight of 131.17 g/mol, indicating that it is quite large compared to other small molecules found in cells.

In terms of its biological properties, leucine is an essential amino acid that cannot be synthesized by the human body and must be obtained from dietary sources. It plays a critical role in protein synthesis, helping to build and repair muscle tissue, among other functions.

Additionally, leucine is involved in regulating energy metabolism and has been shown to activate a signaling pathway called the mammalian target of rapamycin (mTOR), which is involved in muscle protein synthesis and growth.

The Importance of Leucine

Leucine importance

Leucine is an indispensable component of human nutrition and plays a vital role in maintaining overall health and well-being. It is commonly found in dietary sources such as meat, eggs, and dairy products, as well as in plant-based sources such as soybeans, nuts, and seeds.

Supplementation with leucine has also been investigated for its potential benefits in promoting muscle growth and recovery, particularly in athletes and elderly individuals who may be at risk for muscle wasting and sarcopenia.

Overall, the unique structure and properties of leucine make it an important amino acid for a variety of biological processes and essential for supporting overall health and wellness.

Molecular Properties

Molecular Structure

Understanding molecular structure is critical to determining the properties of a substance. Properties such as, chemical reactivity and physical state, can be attributed to the molecular structure of a compound. A molecule’s properties are the result of the arrangement of its atoms and the nature of the chemical bonds between them.

The Role of Chemical Bonds

Chemical Bond

The nature and strength of the chemical bonds formed between atoms are critical in determining the molecule’s properties. Covalent bonds are formed when atoms share electrons, which can be either polar or nonpolar. A polar covalent bond can generate a partial charge on each atom of the bond, resulting in a dipole moment. This dipole moment can give a molecule polar properties, such as the capacity to dissolve in water, as in the case of glucose. In contrast, nonpolar covalent bonds do not generate a dipole moment, which would result in a nonpolar molecule such as methane that is hydrophobic.

Molecular Shapes

Molecular Geometry

Molecular shape is also important to determining the molecule’s properties. Because the electrons in a system repel each other, different molecules are held together at specific angles. This angle depends on several factors like the number of bonds and lone electrons that an individual atom has. The shape of the molecule has a significant impact on how it interacts with other molecules. For instance, the shape of a protein determines how it can interact with other proteins as well as its function. If the shape is changed even by a small amount, then the ability to interact and function will also be changed.

Molecular Polarity

Molecular Polarity

Molecular polarity is a significant factor in the existence of intermolecular forces. Polarity can also affect the molecule’s physical characteristics, such as its boiling and melting points, as well as its solubility in particular solvents. Molecules with the same molecular weight but different polarities will have different boiling points, for instance, nonpolar substances such as oil, have higher boiling points than water.

Molecular Interactions

Molecular Interaction

The chemical and physical properties of a molecule are determined by its interactions with other molecules. Molecules interact with each other through noncovalent interactions, such as hydrogen bonds, van der Waals forces, and dipole-dipole interactions. These interactions affect intermolecular forces which, in turn, affect the physical characteristics of materials such as viscosity, boiling point, and melting point. The intermolecular forces that determine these properties are impacted by the properties of each interacting molecule, which once more are determined by their structures, chemical bonding, and polarity.

Understanding molecular structure is essential for understanding the properties and behavior of substances. A molecule’s characteristics are a result of its individual components and they interact with one another. The components include chemical bonding, intermolecular forces, and molecular arrangement, and these factors contribute to chemical reactivity, physical characteristics, and other properties that are important in chemical and biological systems.

Selecting the Best Description of the Molecule Shown Below


Identifying and understanding molecular structures are essential skills in the field of chemistry. Scientists utilize this knowledge to develop new drugs, create novel materials, and improve manufacturing processes. However, selecting the best description of a molecule can be challenging, particularly for beginners. The molecule shown above is a perfect example. Therefore, in this article, we will discuss how to select the best description of a molecule through its Lewis structure, resonance structures, and molecular geometry.

Lewis Structure

Lewis Structure

The first step in selecting the best description of a molecule is to draw its Lewis structure. The Lewis structure helps determine the number of valence electrons, the number of bonds, and the formal charge of each atom in the molecule. In the molecule above, we have one oxygen atom with six valence electrons (group 6) and two sulfur atoms, each with six valence electrons (group 6). Therefore, the total number of valence electrons is 18 (6+6+6).

The Lewis structure of the molecule shows bonds between the oxygen atom and each sulfur atom. Oxygen has two lone pairs of electrons while each sulfur atom has one lone pair of electrons. The formal charge of each oxygen and sulfur atom in the molecule is zero.

Resonance Structures

Resonance Structures

After drawing the Lewis structure, we can evaluate the possible resonance structures of the molecule. Resonance structures are critical in selecting the best description of a molecule as they show the delocalization of electrons in the molecule. The molecule above has two possible resonance structures that show the double bond alternates between the oxygen and sulfur atoms. Therefore, both sulfur atoms share the negative charge equally. Consequently, the molecule’s real structure is a combination of the two resonance structures.

Molecular Geometry

Molecular Geometry

The final step in selecting the best description of a molecule is evaluating its molecular geometry. Molecular geometry describes the arrangement of atoms in space around the molecule, which affects the molecule’s physical and chemical properties. To determine the molecular geometry, we use the valence shell electron pair repulsion (VSEPR) theory.

In the molecule above, two sulfur atoms share a double bond with the oxygen atom, and the oxygen atom has two lone pairs of electrons. Therefore, the molecular geometry of the molecule is trigonal planar, as there are three electron pairs around the central oxygen atom and no lone electron pairs around the sulfur atoms.


Properly identifying and understanding molecular structures is crucial to the field of chemistry. It allows scientists to predict and explain the physical and chemical properties of a molecule. In addition, molecular structures provide a foundation for the design of new drugs, creation of new materials, and improvement of manufacturing processes. Therefore, it is essential to develop the skills to select the best description of a molecule by evaluating its Lewis structure, resonance structures, and molecular geometry.

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