Lec-10 I Optical Activity in Lactic acid, tartaric acid I Applied Chemistry I Chemical Engineering

Chemical Engineering Department_LJIET
29 Jul 202114:14
EducationalLearning
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TLDRThe video lecture from Yoshi at Angie Institute of Engineering and Technology delves into the fundamentals of stereochemistry, exploring optical isomers, enantiomers, and diastereomers with examples. It explains the concept of plane polarized light and its significance in distinguishing between these isomers. The lecture also introduces the polarimeter, an instrument used to measure optical activity and differentiate between optical isomers based on their effect on polarized light, such as dextrorotatory and levorotatory compounds, and optically inactive ones.

Takeaways
  • 📘 Applied Chemistry is the subject with the code 3130506, and the lecture series focuses on stereochemistry.
  • 🔍 Stereochemistry is the study of the three-dimensional arrangement of atoms in molecules, including optical isomers, enantiomers, and diastereomers.
  • 🌟 Enantiomers are a pair of stereoisomers that are non-superimposable mirror images of each other, like left and right hands.
  • 🌟 Diastereomers are stereoisomers that are not mirror images of each other, resulting from different configurations at one or more chiral centers.
  • 💡 Plane polarized light is light in which all the wave vibrations occur in a single plane, as opposed to non-polarized or unpolarized light where vibrations occur in multiple directions.
  • 🔄 Polarization is the process of converting non-polarized light into polarized light, using a polarizer such as a prism or a Nicol prism.
  • 🔍 Chirality refers to the property of a molecule that makes it non-superimposable on its mirror image, often due to the presence of a chiral carbon atom bonded to four different groups.
  • 📈 The plane of symmetry is an imaginary plane that divides an object into two mirror-image parts, which is a key concept in understanding chirality and optical activity.
  • 🧪 Optical activity is the ability of certain molecules to rotate the plane of polarized light, and it is measured using an instrument called a polarimeter.
  • 🌀 The rotation of plane polarized light can be either clockwise (dextrorotatory, denoted as + or d) or counterclockwise (levorotatory, denoted as - or l), indicating the compound's optical activity.
  • 🧬 Lactic acid and tartaric acid are examples of compounds with chiral centers that exhibit optical activity, having different forms like dextrorotatory and levorotatory isomers.
Q & A

  • What is the subject code for Applied Chemistry in the lecture series?

    -The subject code for Applied Chemistry is 3130506.

  • What is the significance of enantiomers in stereochemistry?

    -Enantiomers are a type of optical isomers that are non-superimposable mirror images of each other. They are significant in stereochemistry because they can interact differently with plane polarized light, leading to different optical activities.

  • What are diastereomers and how do they relate to stereochemistry?

    -Diastereomers are stereoisomers that are not mirror images of each other. They occur in molecules with multiple chiral centers when not all chiral centers have the same configuration. In stereochemistry, diastereomers can have different physical and chemical properties and can be separated based on their behavior towards plane polarized light.

  • What is plane polarized light and how does it differ from non-polarized light?

    -Plane polarized light is light in which the vibrations occur in a single plane. This contrasts with non-polarized or unpolarized light, where the light waves vibrate in every direction. Plane polarized light is important in the study of optical isomers as it can be used to distinguish between different types of stereochemistry.

  • What is the process of converting non-polarized light to plane polarized light called?

    -The process of converting non-polarized light to plane polarized light is known as polarization. This is typically achieved using a polarizer, which can be a prism or other specialized material that allows only light vibrating in a specific plane to pass through.

  • What is a plane of symmetry in the context of stereochemistry?

    -A plane of symmetry in stereochemistry is a hypothetical plane that divides a molecule into two mirror-image halves. If a molecule has a plane of symmetry, it is not chiral and does not exhibit optical activity.

  • What is chirality and how is it related to optical activity?

    -Chirality refers to the property of a molecule that makes it non-superimposable on its mirror image. Molecules with chirality, particularly those with chiral carbon atoms, can exhibit optical activity, meaning they can rotate plane polarized light, which is a key concept in the study of stereochemistry.

  • How is optical activity measured in compounds?

    -Optical activity in compounds is measured using an instrument called a polarimeter. This device allows the determination of how much a compound rotates plane polarized light, which is indicative of its optical activity.

  • What are the different types of optical rotation that can be observed with optically active compounds?

    -Optically active compounds can exhibit either dextrorotatory (clockwise) or levorotatory (counterclockwise) rotation of plane polarized light. If there is no rotation, the compound is considered optically inactive.

  • How does the structure of lactic acid relate to its optical activity?

    -Lactic acid contains a chiral carbon atom, making it a chiral molecule. It exists in two mirror-image forms, d-lactic acid and l-lactic acid, which are non-superimposable and exhibit different optical activities. The presence of the chiral carbon atom is what confers optical activity to lactic acid.

  • What are the four different forms of tartaric acid mentioned in the script?

    -The four different forms of tartaric acid mentioned are dextrorotatory (d plus), levorotatory (l minus), meso (resonate), and a form that is optically inactive. These forms differ in the configuration of their chiral centers and their ability to rotate plane polarized light.

Outlines
00:00
🔬 Introduction to Stereochemistry and Polarized Light

Yoshi, from Angie Institute of Engineering and Technology, introduces the video lecture series on Applied Chemistry, focusing on stereochemistry, which is the study of how molecular structures differ in space. The lecture delves into the basics of stereochemistry, including the concepts of optical isomers, enantiomers, and diastereomers, using examples to illustrate these differences. A significant part of the lecture is dedicated to explaining plane polarized light, differentiating it from non-polarized light. Plane polarized light vibrates in a single plane, unlike non-polarized light, whose vibrations occur in multiple directions. The process of converting non-polarized light to plane polarized light, known as polarization, and the role of polarizers, such as prisms, are explained. The lecture emphasizes the importance of understanding plane polarized light to grasp the fundamental concepts of stereochemistry.

05:02
🌐 Plane of Symmetry, Chirality, and Optical Activity Measurement

This section explores further concepts essential to stereochemistry, such as the plane of symmetry and chirality. The plane of symmetry refers to a plane that divides a compound into two symmetrical parts. Chirality is introduced through the concept of a chiral carbon atom, which is bonded to four different substituents, making the compound optically active. Yoshi uses examples to clarify these concepts, highlighting how chiral compounds are non-superimposable mirror images of each other and thus are optically active. The lecture transitions to discussing how optical activity is measured using a polarimeter. The process involves converting unpolarized light to plane polarized light, which then passes through a sample. The polarimeter can detect the rotation of plane polarized light caused by optically active compounds, classifying them as dextrorotatory or levorotatory based on the direction of rotation.

10:04
🧪 Optical Activity in Compounds and Summary

In the concluding section, Yoshi demonstrates the concept of optical activity through the example of lactic acid, explaining how its chiral carbon leads to two forms: D and L lactic acid, which are mirror images of each other but non-superimposable. This principle extends to tartaric acid, which showcases multiple forms of optical activity, including dextrorotatory, levorotatory, and optically inactive forms. The lecture emphasizes understanding the structural basis of optical activity and its measurement, concluding with a demonstration of how polarimetry is used to distinguish between different optical isomers of compounds like lactic acid and tartaric acid. The comprehensive overview ties together the importance of stereochemistry in understanding the behavior of compounds in relation to polarized light.

Mindmap
Keywords
💡Stereochemistry
Stereochemistry is a branch of chemistry that focuses on the three-dimensional shape of molecules and the effects of these shapes on the properties and reactivity of the molecules. In the video, the concept of stereochemistry is introduced as the foundational knowledge for understanding optical isomers, enantiomers, and diastereomers. It is crucial for comprehending the spatial arrangement of atoms in molecules and how it influences their behavior, particularly in relation to plane polarized light.
💡Optical Isomers
Optical isomers are molecules that are mirror images of each other but cannot be superimposed, similar to a pair of hands. They have the same molecular formula and structure but differ in the way they interact with plane polarized light. In the context of the video, optical isomers are a key concept in understanding the behavior of molecules in applied chemistry, especially in relation to their interaction with light and their separation methods.
💡Enantiomers
Enantiomers are a pair of stereoisomers that are non-superimposable mirror images of each other. They have the same physical and chemical properties, except when they interact with plane polarized light or with other chiral molecules. In the video, enantiomers are discussed as a fundamental concept in stereochemistry, with their ability to rotate plane polarized light in opposite directions being a key characteristic.
💡Diastereomers
Diastereomers are stereoisomers that are not mirror images of each other. They have the same molecular formula but differ in the spatial arrangement of their atoms. Unlike enantiomers, diastereomers do not have a mirror-image relationship and can be distinguished in ways other than their interaction with plane polarized light. In the video, diastereomers are mentioned as part of the broader discussion on stereoisomers and their different properties and behaviors.
💡Plane Polarized Light
Plane polarized light is light whose electric field vector vibrates in a single plane. It is a type of polarized light that can be obtained by filtering natural light through a polarizing filter. In the video, plane polarized light is essential for understanding the optical activity of molecules and how they can be separated based on their interaction with this type of light.
💡Polarizer
A polarizer is a device or material that transmits light waves vibrating in a particular direction while blocking other directions of vibration. It is used to convert unpolarized light into plane polarized light. In the video, the polarizer plays a crucial role in the study of optical isomers, as it helps in determining the optical activity of compounds by analyzing how they interact with plane polarized light.
💡Chirality
Chirality refers to the property of a molecule that makes it non-superimposable on its mirror image. Molecules with chirality are called chiral molecules, and they often have a central carbon atom bonded to four different groups. In the video, chirality is a critical concept for understanding the optical activity of compounds and their behavior in the presence of plane polarized light.
💡Optically Active Compounds
Optically active compounds are molecules that can rotate the plane of polarized light either to the right (dextrorotatory) or to the left (levorotatory). This property is due to the presence of chiral centers within the molecule. In the video, optically active compounds are discussed as a key aspect of stereochemistry, with their ability to rotate plane polarized light being a defining characteristic.
💡Polarimeter
A polarimeter is an instrument used to measure the angle of rotation of plane polarized light by an optically active substance. It is a crucial tool in determining the optical activity of compounds. In the video, the polarimeter is introduced as the device that helps in quantifying the optical activity of compounds, which is essential for distinguishing between different optical isomers.
💡Plane of Symmetry
A plane of symmetry is an imaginary plane that divides an object into two mirror-image halves. If an object can be folded along this plane and the two halves match exactly, the object is said to have a plane of symmetry. In the context of the video, the concept of a plane of symmetry is used to describe the symmetry in molecules and how it relates to their optical activity and the possibility of them being chiral.
💡Dextrorotatory
Dextrorotatory, often denoted as d- or +, refers to the rotation of plane polarized light in a clockwise direction by an optically active compound. This term is used to describe the specific type of optical activity exhibited by certain molecules. In the video, dextrorotatory compounds are mentioned as those that rotate the plane of polarized light towards the right, which is a key characteristic used to identify and differentiate optical isomers.
💡Levorotatory
Levorotatory, often denoted as l- or -, refers to the rotation of plane polarized light in a counter-clockwise direction by an optically active compound. This term is used to describe the specific type of optical activity exhibited by certain molecules. In the video, levorotatory compounds are mentioned as those that rotate the plane of polarized light towards the left, which is a key characteristic used to identify and differentiate optical isomers.
Highlights

Introduction to Applied Chemistry and subject code 3130506

Discussion on Stereochemistry and its basics

Explanation of optical isomers and enantiomers with examples

Definition and understanding of diastereomers

The concept of plane polarized light and its difference from non-polarized light

Process of polarization and the role of polarizers

Introduction to the plane of symmetry in compounds

Explanation of chirality and its significance in organic compounds

Identification of chiral carbon and its impact on optical activity

Measurement of optical activity using a polarimeter

Description of the working principle of a polarimeter

Differentiation between dextrorotatory and levorotatory compounds

Explanation of optically inactive compounds

Observation of optical activity in lactic acid

Discussion on the structures of d and l lactic acid, and their mirror images

Explanation of different forms of optical isomers in tartaric acid

Understanding of the meso form and its optical inactivity

Transcripts

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StereochemistryOptical IsomersChiralityPolarized LightEnantiomersDiastereomersPolarimeterChemical StructuresLactic AcidTartaric Acid