Podcast
Questions and Answers
Which condition is NOT necessary for a molecule to exhibit geometrical isomerism?
Which condition is NOT necessary for a molecule to exhibit geometrical isomerism?
- Presence of a restricted rotation around a bond.
- The molecule can be separated into distinct isomers.
- Restricted site must have different groups.
- Areal distance must be different. (correct)
Which of the following best describes geometrical isomers?
Which of the following best describes geometrical isomers?
- They are also known as diastereomers, which are non-superimposable. (correct)
- They are also known as enantiomers, which are non-superimposable.
- They are also known as enantiomers, which can be superimposed.
- They are also known as diastereomers, which are mirror images.
For a molecule exhibiting cis-trans isomerism, which statement accurately describes the arrangement of similar groups in the 'cis' isomer?
For a molecule exhibiting cis-trans isomerism, which statement accurately describes the arrangement of similar groups in the 'cis' isomer?
- Similar groups are oriented on opposite sides of the double bond.
- Similar groups are oriented on the same side of the double bond. (correct)
- Similar groups are oriented perpendicular to each other.
- There are no similar groups in cis isomers.
According to the E/Z system for nomenclature of geometrical isomers, what determines the priority of substituents on a double bond?
According to the E/Z system for nomenclature of geometrical isomers, what determines the priority of substituents on a double bond?
In cases where the first atom of substituents on a double bond has the same atomic number, how is the priority for E/Z nomenclature determined?
In cases where the first atom of substituents on a double bond has the same atomic number, how is the priority for E/Z nomenclature determined?
For isotopes of the same element attached to a double bond, which isotope receives higher priority in E/Z nomenclature?
For isotopes of the same element attached to a double bond, which isotope receives higher priority in E/Z nomenclature?
When comparing different types of multiple bonds for priority in the E/Z system, which of the following orders is correct, indicating higher priority to lower priority?
When comparing different types of multiple bonds for priority in the E/Z system, which of the following orders is correct, indicating higher priority to lower priority?
What structural feature is essential for syn-anti isomerism in oximes (compounds containing a $C=N$ bond)?
What structural feature is essential for syn-anti isomerism in oximes (compounds containing a $C=N$ bond)?
What is the primary difference between syn and anti isomers in oximes, specifically when considering the spatial arrangement of substituents?
What is the primary difference between syn and anti isomers in oximes, specifically when considering the spatial arrangement of substituents?
What type of compounds exhibit geometrical isomerism due to the presence of a $N=N$ bond?
What type of compounds exhibit geometrical isomerism due to the presence of a $N=N$ bond?
Under what condition will a molecule NOT exhibit geometrical isomerism?
Under what condition will a molecule NOT exhibit geometrical isomerism?
What is the defining characteristic of stereocenters in a molecule regarding their ability to exhibit stereoisomerism?
What is the defining characteristic of stereocenters in a molecule regarding their ability to exhibit stereoisomerism?
What is the specific criterion necessary for a carbon atom to be considered chiral?
What is the specific criterion necessary for a carbon atom to be considered chiral?
In the context of assigning R/S configurations, which of the following terms is associated with the configuration where the priority sequence proceeds in a counterclockwise direction?
In the context of assigning R/S configurations, which of the following terms is associated with the configuration where the priority sequence proceeds in a counterclockwise direction?
What term is denoted to a compound that is optically active and rotates plane-polarized light to the right (clockwise)?
What term is denoted to a compound that is optically active and rotates plane-polarized light to the right (clockwise)?
Flashcards
What causes geometrical isomerism?
What causes geometrical isomerism?
Arises due to restricted rotation around C=C, C=N, C=O, N=N rings
Cis-Trans Isomers
Cis-Trans Isomers
Cis: similar groups are on the same side. Trans: similar groups are on opposite sides.
E/Z System
E/Z System
Z (Zusammen): higher priority groups are on the same side. E (Entgegen): higher priority groups are on opposite sides.
Priority Determination
Priority Determination
Signup and view all the flashcards
Isotope Priority
Isotope Priority
Signup and view all the flashcards
Syn/Anti Isomers
Syn/Anti Isomers
Signup and view all the flashcards
Chiral Center
Chiral Center
Signup and view all the flashcards
Stereocenter
Stereocenter
Signup and view all the flashcards
Identical
Identical
Signup and view all the flashcards
Enantiomers
Enantiomers
Signup and view all the flashcards
Diastereomers
Diastereomers
Signup and view all the flashcards
Meso Compound
Meso Compound
Signup and view all the flashcards
Racemic Mixture
Racemic Mixture
Signup and view all the flashcards
Cumulenes Isomerism
Cumulenes Isomerism
Signup and view all the flashcards
Pseudo Chiral Carbon
Pseudo Chiral Carbon
Signup and view all the flashcards
Study Notes
- Geometrical isomerism arises from restricted rotation around C=C, C=N, C=O, N=N, and ring structures.
- Geometrical isomers, also known as diastereomers, can be separated.
- Areal distance must be different between groups on the restricted site.
- The restricted site must have different groups.
Cis-Trans Isomerism
- For cis isomers, similar groups are on the same side.
- For Trans isomers, similar groups are on opposite sides.
Z/E System
- Assigns priority based on the atomic number of the substituents.
- Z (Zusammen) isomers have higher priority groups on the same side.
- E (Entgegen) isomers have higher priority groups on opposite sides.
- If the atomic number of the first atom is the same, compare subsequent atoms.
Isotopes
- In the case of isotopes, higher mass number gets higher priority.
- The priority of atom involvement is: C≡C > C=C > C=C, C=N > CH=NH, C=O > C=O
Syn-Anti Isomerism (Applies to Compounds Having Any Chiral Carbons)
- Occurs with C=N and N=N bonds.
- Syn isomers have specific groups on the same side, while anti isomers have them on opposite sides.
- Aldoximes
- R-CH=NOH structure
- Ketoximes
- R1R2C=NOH structure
Types of GI (N=N) (azo Compounds)
- N=N compounds
Calculation of Geometrical Isomers
- If a molecule lacks symmetry, the total number of geometrical isomers (GI) is 2n, where 'n' is the number of stereogenic centers (sites that exhibit GI).
- If a molecule possesses symmetry, the total number of GI is given by 2n-1 + 2(p-1) where p = n/2 if n is even, or p = (n+1)/2 if n is odd.
Optical Isomerism
- A chiral center is a sp3 atom attached to 4 different groups.
- Chiral centers include chiral carbon, phosphorus, nitrogen, oxygen, and sulfur.
- All chiral centers are stereocenters, but not all stereocenters are chiral centers.
- Plane of symmetry divides the molecule into two equal halves.
- Center of symmetry is a point from which diagonally opposite lines meet.
Relation Between Molecules with Chirality
- Enantiomers
- A non-superimposable mirror image.
- Diastereomers
- Not mirror images.
- Identical
- The same structure.
- Meso compounds
- Compounds with two or more chiral centers but also have a plane of symmetry.
D/L System (Relative Configuration)
- Used for biomolecules.
- Assigns configuration of minor images.
- Read the Fischer projection formula with maximum carbon on the vertical line and highest oxidized group on top.
- Oxidized Group Priority: COOH > CHO > CH2OH
- D/L is not used for symmetrical molecules
- Looking at the last chiral carbon, if it contains OH/NH2 at right, then D; if at left, then L.
- If both OH and NH2 are present, then D/L is decided by CHO/COOH respectively.
Threo and Erythro Isomers
- Similar groups on the same side define Erythro isomers.
- Similar groups on the opposite side define threo isomers.
- Stereoisomers are applicable for compounds having any chiral carbon.
Racemic Mixtures
- Racemic mixture contains aquimolar mixture of two minor images.
Cumulenes (Odd No. Bond)
- Cumulenes with an even number of cumulative double bonds may exhibit optical isomerism.
- Optically active when A ≠B and D ≠E.
Spiro Compounds
- Spiro compounds with an even number of rings can exhibit optical isomerism.
Optical Isomer Calculation
- If a molecule is unsymmetrical, the total number of optical isomers is 2n (where n = number of chiral centers). The number of optically active isomers is also 2n.
- If a molecule is symmetrical, use the following formulas:
- If n is even:
- Total Optical Isomers: 2n
- Total Activities : 2n-1 + 2(p-1)
- Meso: 2p-1
- RM (Racemic Mixture) = O.A/2
- If n is odd:
- Total Optical Isomers: 2n
- Total Activities: 2(p/2)
- Meso: 2(p/2)
- RM (Racemic Mixture) = OA/2
- If n is even:
Pseudo Chiral Carbon
- A carbon with two different groups and other two groups being the same but exhibiting GI.
- A carbon that exhibits GI or has a chiral carbon.
Optical Rotation
- Depends on concentration of solution (gm/ml) and length of the tube (dm).
Specific Rotation
- Rotation observed when 0.5g of organic solution in 1mL and the length of tube is 1dm with the formula:
- α = θ/(C*L)
- C = Conc, (gm/ml)
- L = Length (dm)
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
