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Molecular Shapes&Isomerism

Objectives

  • Understand the 3-dimensional nature of molecules
  • Learn about Molecular Symmetry
  • Be able to identify the various isomers possible for one molecular formula
  • Be able to identify enantiomers

Grading

  • Quiz (10%).
  • Lab Report Form (90%).

Before Coming to Lab . . .

Look over the following to make sure you have a basic understanding of the topics presented.

  • Drawing Lewis Structures
  • Determining the Shapes of Molecules from their Lewis Structures
  • Some Basic Aspects of Bonding
  • Model Kits

Introduction

The shape of a molecule is extremely important in determining its physical properties and reactivity. A multitude of shapes are possible, and in today’s lab, you will be looking at several.

In Part 1, you will be exploring the various symmetry elements that can be present in molecules. The symmetry elements you will be looking for are mirror planes, rotation axes, and inversion centers. Being able to determine which symmetry elements are present in a molecule help in understanding its chemistry. If there is a plane present in the molecule that has the exact same arrangement of atoms on either side of the plane, then the molecule has a mirror plane ( σ ) . It is important to note that a molecule can have more than one mirror plane. Rotation axes are represented as C n (n = 1, 2, 3 . . .). The subscript indicates how many degrees of rotation (360 o /n) are needed in order to return to the same orientation of atoms with which you started. So if there is a C 2 axis, the rotation would be 180 o . An example of a molecule having a C 2 axis is H 2 O.

The third symmetry element is an inversion center (i) . In such molecules, starting at any position and drawing a line through the center and an equal distance to the opposite side of the molecule, you will end up at a position with an identical environment to the one you started from.

Part 2 of the lab introduces the concept of enantiomers. Enantiomers are molecules sharing the same molecular configuration, but they are non-superimposable images of each other. This concept should become clearer as you build the models for this part of the lab. Enantiomers share many of the same physical properties. The property which distinguishes them is the direction in which they rotate plane-polarized light. They will rotate the light in equal amounts but in different directions ( plane-polarized light is just light in which all wave vibrations have been filtered out except for those in one plane ). If both enantiomers are present in a 1:1 ratio, the effects of the rotation of light cancel and no net rotation is observed. Such a mixture of isomers is known as a racemic mixture or as a racemate . Because these isomers rotate plane-polarized light, they are also known as optical isomers . Compounds that form optical isomers are said to be chiral .

The chemistry of enantiomers is of great importance in the field of medicine. It has been discovered that with many drugs, one enantiomer will be biologically active while the other will be inactive or even produce undesired side effects. For this reason, it has become advantageous for pharmaceutical companies to try to synthesize the active enantiomer exclusively.

Questions & Answers

Discuss the differences between taste and flavor, including how other sensory inputs contribute to our  perception of flavor.
John Reply
taste refers to your understanding of the flavor . while flavor one The other hand is refers to sort of just a blend things.
Faith
While taste primarily relies on our taste buds, flavor involves a complex interplay between taste and aroma
Kamara
which drugs can we use for ulcers
Ummi Reply
omeprazole
Kamara
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Renee
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Renee
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Kamara
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Kamara
Omeprazole Cimetidine / Tagament For the complicated once ulcer - kit
Patrick
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Nency Reply
Not really sure
Eli
to drain extracellular fluid all over the body.
asegid
The lymphatic system plays several crucial roles in the human body, functioning as a key component of the immune system and contributing to the maintenance of fluid balance. Its main functions include: 1. Immune Response: The lymphatic system produces and transports lymphocytes, which are a type of
asegid
to transport fluids fats proteins and lymphocytes to the blood stream as lymph
Adama
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Oyindarmola Reply
Anatomy is the identification and description of the structures of living things
Kamara
what's the difference between anatomy and physiology
Oyerinde Reply
Anatomy is the study of the structure of the body, while physiology is the study of the function of the body. Anatomy looks at the body's organs and systems, while physiology looks at how those organs and systems work together to keep the body functioning.
AI-Robot
what is enzymes all about?
Mohammed Reply
Enzymes are proteins that help speed up chemical reactions in our bodies. Enzymes are essential for digestion, liver function and much more. Too much or too little of a certain enzyme can cause health problems
Kamara
yes
Prince
how does the stomach protect itself from the damaging effects of HCl
Wulku Reply
little girl okay how does the stomach protect itself from the damaging effect of HCL
Wulku
it is because of the enzyme that the stomach produce that help the stomach from the damaging effect of HCL
Kamara
function of digestive system
Ali Reply
function of digestive
Ali
the diagram of the lungs
Adaeze Reply
what is the normal body temperature
Diya Reply
37 degrees selcius
Xolo
37°c
Stephanie
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Mark
36.5
Simon
37°c
Iyogho
the normal temperature is 37°c or 98.6 °Fahrenheit is important for maintaining the homeostasis in the body the body regular this temperature through the process called thermoregulation which involves brain skin muscle and other organ working together to maintain stable internal temperature
Stephanie
37A c
Wulku
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Diya Reply
anaemia is the decrease in RBC count hemoglobin count and PVC count
Eniola
what is the pH of the vagina
Diya Reply
how does Lysin attack pathogens
Diya
acid
Mary
I information on anatomy position and digestive system and there enzyme
Elisha Reply
anatomy of the female external genitalia
Muhammad Reply
Organ Systems Of The Human Body (Continued) Organ Systems Of The Human Body (Continued)
Theophilus Reply
what's lochia albra
Kizito
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Source:  OpenStax, Gen chem lab. OpenStax CNX. Oct 12, 2009 Download for free at http://cnx.org/content/col10452/1.51
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