Question

Among the common inhaled anesthetics are halothane: \(\mathrm{CF}_{3} \mathrm{CHClBr}\) enflurane: CHFClCF \(_{2} \mathrm{OCHF}_{2}\) isoflurane: \(\mathrm{CF}_{3} \mathrm{CHClOCHF}_{2}\) methoxyflurane: \(\mathrm{CHCl}_{2} \mathrm{CF}_{2} \mathrm{OCH}_{3}\) Draw Lewis structures of these molecules.

Short answer

Lewis structures are graphical representations of the bonds between atoms and depict the lone pair of electrons in molecules. In this exercise, Lewis structures for Halothane, Enflurane, Isoflurane and Methoxyflurane have been drawn considering the number of valence electrons and the types of bonds they can form to adhere to the octet rule.

Step-by-step solution

Understand Lewis Structures

To start drawing the Lewis structures, it's fundamental to understand the concept. A Lewis dot structure is a graphical representation of the molecular structure of a chemical compound where all the valence electrons participating in forming bonds are represented by dots around the atomic symbols. First, locate each atom in the periodic table to determine the number of valence electrons.

Draw Lewis structure for Halothane (\(CF_{3}CHClBr\))

Start with Carbon atom (C) at the center as it can form four bonds. Connect three Fluorine atoms (F) and one Hydrogen atom (H) to it. Each F and H atom complete their octet/sextet by taking up one electron from Carbon. Now carbon is connected to Chlorine (Cl) and then to Bromine (Br) atom respectively, with both completing their octet by forming one bond with their neighbors.

Draw Lewis structure for Enflurane (\(CHFClCF_{2}OCHF_{2}\))

Again place Carbon (C) at the center and connect one Hydrogen (H), one Fluorine (F), one Chlorine (Cl), and a Carbon (C). All of these atoms complete their octet/sextet by taking one electron from the central Carbon atom. The second Carbon atom is then connected to two Fluorine atoms and further to Oxygen. A final Carbon atom is attached to the Oxygen, and the structure ends with four attachments: two Fluorine atoms and one Hydrogen.

Draw Lewis structure for Isoflurane (\(CF_{3}CHClOCHF_{2}\))

Start with the Carbon (C) atom at the center and connect it to three Fluorine (F) atoms and one Hydrogen (H). Then, attach Carbon to Chlorine (Cl) and then Oxygen (O). The structure is completed by attaching a Carbon to the Oxygen, with two Fluorine and one Hydrogen bonded to it.

Draw Lewis structure for Methoxyflurane (\(CHCl_{2}CF_{2}OCH_{3}\))

Starting with Carbon at the center, attach one Hydrogen, and two Chlorine atoms. Further connects to another Carbon atom attached to two Fluorine atoms. This Carbon is connected to Oxygen and finally ends with attaching a Carbon bound to three Hydrogen atoms and one Oxygen atom.

Key concepts

Valence Electrons

Valence electrons are pivotal when considering Lewis structures. They are the electrons in the outermost shell of an atom, serving as potential participants in chemical bonds. Identifying these electrons is the first step in drawing any Lewis structure.
To determine the valence electrons, look up each element on the periodic table:

• Carbon (C) has 4 valence electrons.
• Fluorine (F) has 7 valence electrons.
• Chlorine (Cl) and Bromine (Br) also contribute 7 valence electrons each.
• Hydrogen (H), with just 1 valence electron, fits into forming simple bonds.

Valence electrons define the bonding capacity of elements and help visualize which atoms can connect, facilitating the drawing of Lewis structures. This concept ensures that all atoms fulfill their desired electron configuration, achieving stability by completing their octet (except for Hydrogen, which seeks a duet). Each bond can be counted as two shared electrons, providing insight into the molecular structure.

Halothane

Halothane is a widely used anesthetic represented by the chemical formula \(\mathrm{CF}_3\mathrm{CHClBr}\). Producing its Lewis structure starts by focusing on the central carbon (C) atom. Carbon can form four bonds, making it an ideal centerpiece for organizing attached elements around it.
The structure features:

• Three fluorine (F) atoms attached to the central carbon, each requiring one extra electron to fulfill their octet.
• A hydrogen atom (H) also bonded to the carbon, which needs just one electron for a duet.
• A chlorine (Cl) and a bromine (Br) atom, each respectively fulfilling their octets by forming single bonds with the central carbon.

Understanding these connections helps you visualize how electrons are shared in the molecule, maintaining the stability and unique attributes of halothane as an inhaled anesthetic.

Enflurane

Enflurane, chemically denoted as \(\mathrm{CHFClCF_{2}OCHF_{2}}\), has a complex molecular geometry. In this molecule, the arrangement of atoms around central carbons is crucial for deciphering its structure. The primary focus is on the carbon atoms, which dictate connectivity within the molecule.
Key points in the structure include:

• The first carbon is central, bonded to a fluorine (F), a hydrogen (H), and a chlorine (Cl), each requiring single bonds to complete their electron requirements.
• A subsequent carbon links to the first, bonded to two fluorine atoms and an oxygen.
• The oxygen atom is a pivotal connector here, bridging to the third carbon chain that also binds to two additional fluorine atoms and one hydrogen.

Each atom achieves a stable configuration, highlighting the precision required when drawing enflurane’s structure. The connections emphasize the molecule's complexity as an anesthetic with critical medical applications.

Molecular Structure

Molecular structure is a fundamental concept that provides a 3D visualization of how atoms arrange within a molecule. By drawing Lewis structures, one gets the primary idea of the structural skeleton, although it is primarily a 2D representation. However, it sets the stage for understanding the actual 3D shape.
When approaching molecular structure:

• Consider which atom forms the center base around which other atoms are organized. Carbon, for instance, often serves this purpose due to its ability to form multiple bonds.
• Evaluate how lone pairs of electrons and bonding pairs influence the geometry, leading to variations such as linear, bent, trigonal planar, or tetrahedral shapes.
• Note that bond angles and electron repulsions affect the final shape and properties of the molecule.

The ability of Lewis structures to illustrate molecular structure allows for predicting physical and chemical behaviors. Key applications include determining reactivity, polarity, and even biological activity in the case of anesthetics like halothane and enflurane.