Organic Chemistry Exam III Chapter 4 Open Book ✓ Solved
Organic Chemistry Exam III Chapter 4 Open Book Name:
List the substituents shown below in order of relative priority from greatest to smallest: -OH, -COOH, -CH3, -C=CHCH2CH3, -CH=CH.
Using IUPAC nomenclature and syntax, name the compound shown below. Include in the compound’s name the Z or E configuration.
Does the following compound have a R or S configuration and why?
How would the compound shown below affect plane polarized light?
A solution containing 5.0g of compound dissolved in 1000mL of solvent generated an observed rotation of plane-polarized light (λ = 589.6nm) of 27° in a polarimeter tube 250mm long at a temperature of 25°C. What is the specific rotation of the compound?
How many asymmetric centers does the compound shown below have?
Are the molecules shown below enantiomers, diastereomers, constitutional isomers, or identical?
Using IUPAC nomenclature and syntax, name the compound shown below. Include in the compound’s name the Z or E configuration.
Are the molecules shown below enantiomers, diastereomers, constitutional isomers, or identical?
Are the molecules shown below enantiomers, diastereomers, constitutional isomers, or identical?
Paper For Above Instructions
Organic chemistry plays a foundational role in understanding the complex nature of matter. Each question presented in this examination explores a different facet of organic chemical principles, from nomenclature and stereoisomerism to their capacity for optical activity. Through a systematic approach, each question will be addressed, showcasing both reasoning and applicability of organic chemistry concepts.
1. Relating Substituent Priorities
Substituents in organic compounds are often represented in terms of their priority, which is determined by the Cahn-Ingold-Prelog priority rules. According to these rules, the substituents from greatest to smallest priority when considering their atomic numbers and connectivity are:
- -COOH (carboxylic acid group)
- -OH (hydroxyl group)
- -C=CHCH2CH3 (alkene with a longer carbon chain)
- -CH=CH (alkene)
- -CH3 (methyl group)
2. Compound Naming with IUPAC Nomenclature
The naming of compounds in organic chemistry follows the IUPAC nomenclature rules, which involve identifying the longest carbon chain and the substituents attached to it, along with their stereochemistry. If the compound has a configuration as Z or E, it would be vital to indicate this in the name. For example, if we take a compound that has its substituents arranged in accordance with the rules, it may be named as but-2-ene, cis- or trans- depending on the arrangement, or 2-butene (E/Z nomenclature).
3. Determining R or S Configuration
The configuration of a chiral center in a compound can be designated as R (rectus, right) or S (sinister, left) based on the spatial arrangement of the substituents around the chiral center. To determine this, you rank the substituents according to their atomic number/priority, arranging them accordingly. If the priority decreases in a clockwise manner, the configuration is R; if it decreases counterclockwise, it is S. This visual spatial reasoning is essential for understanding stereochemistry.
4. Effect of Compound on Plane Polarized Light
The optical activity of a compound refers to its ability to rotate plane-polarized light, a property exhibited by chiral molecules. The direction and degree of rotation depends on the molecular structure and specific rotation. For a given compound, if it causes clockwise rotation, it is dubbed dextrorotatory (+), and if counterclockwise, levorotatory (-). This property is measurable and is critical for compound identification in polarimetry.
5. Specific Rotation Calculation
Specific rotation ([α]) can be calculated using the formula: [α] = α / (c l), where α is the observed rotation, c is the concentration of the solution in grams per milliliter, and l is the path length in decimeters. In this case, for the observed rotation of +27° with 5.0g in 1000mL, the concentration (c) = (5.0 g / 1000 mL) = 0.005 g/mL, and the tube length (l) = 250 mm = 2.5 dm. Thus, [α] = 27° / (0.005 g/mL 2.5 dm) = 2160°/(g/mL·dm), demonstrating the optical activity of the compound.
6. Asymmetric Centers in the Compound
The identification of asymmetric centers (chiral centers) within a molecule is crucial in stereochemistry. Each asymmetric center corresponds to a carbon atom attached to four different substituents. To determine the total number of such centers, one would analyze the molecular structure and count the carbons that fit this description. The number of asymmetric centers may also influence the number of stereoisomers a compound can have, directly affecting its behavior and reactivity.
7. Classifying Molecular Relationships
When analyzing pairs of molecules, it is important to classify them as enantiomers (non-superimposable mirror images), diastereomers (stereoisomers that are not mirror images), constitutional isomers (differ in connectivity), or identical molecules. This classification is vital for understanding chemical properties and potential reactivity of the compounds in question.
Using IUPAC Nomenclature Again
Once again applying IUPAC principles will require an identification of substituents and proper connectivity once more to arrive at the correct name of the compound in question. For example, if a compound is a substituted alkene, the correct nomenclature will involve both the longest carbon chain accounting the double bond and ensuring the proper stereochemistry Z or E is annotated along with the compound's name.
Conclusion
Each question posed forces a deeper exploration into the functions and behaviors of organic compounds, highlighting aspects of stereochemistry, optical activity, and systematic nomenclature. The structural characteristics often dictate chemical behavior, making this investigation foundational not only for academic purposes but also for practical applications in fields such as pharmaceuticals, materials science, and biochemistry.
References
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