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A chemistry problem asks to find which sample has an enantiomeric excess of about 30%, given the specific rotation of an S enantiomer. A speech bubble says "Solve with Prof. Sonny!" next to a Sonny Angel figure.
Key concepts for solving the problem are presented, including formulas for specific rotation and enantiomeric excess (EE). A Sonny Angel figure is visible on the left.
The chemistry problem is restated, with additional notes highlighting the given specific rotation of the pure S-enantiomer and the EE formula to be used. A Sonny Angel figure is on the right.
The problem is shown with calculations for option A, determining its enantiomeric excess is approximately 44.45%, not 30%. A Sonny Angel figure is on the right.
The problem is shown with calculations for option B, determining its enantiomeric excess is 30%. A Sonny Angel figure is on the right.
The problem is shown with calculations for option C, determining its enantiomeric excess is approximately 50.1%, not 30%. A Sonny Angel figure is on the right.
The problem is shown with calculations for option D, determining its enantiomeric excess is approximately 14.29%, not 30%. A Sonny Angel figure is on the right.
The chemistry problem is displayed with option B circled, indicating it is the correct answer, and a note stating "The answer is B!". A Sonny Angel figure is on the right.
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Solve with Sonny: enantiomeric excess 🧪👼🏻

Back to this tricky topic of EE (hate ts). Given the specific rotation of an S enantiomer we can determine which sample with have an enantiomeric excess of about 30%! This is the kind of question I would have chosen a random answer for on an exam but not anymore- I am a changed Sonny. Some key concepts to remember are that specific rotation= the observed rotation/ cl and EE=([major concentration]-[minor concentration])/ total concentration or EE= observed rotation/the pure concentration. Since we are given the specific rotation of the pure S-enantiomer in the problem we can calculate the observed EE for each sample option using the second EE equation. After solving for EE we can go back and check if our answer equals the 30% from the question. Please don't give up like I did!

Love,

Sonny

#sonnyangel #ochem #stem #uni #premed

2025/1/7 Edited to

... Read moreEnantiomeric excess (EE) is a vital concept in stereochemistry and organic chemistry, particularly when studying chiral molecules and their properties. It allows chemists to quantify the purity of chiral compounds and understand reactions involving enantiomers. To effectively calculate the enantiomeric excess, one must grasp key principles such as specific rotation, which is the observed rotation divided by the path length and concentration. For example, if a compound's pure S-enantiomer has a specific rotation of +60.0°, and you're presented with experimental data showing observed rotations from different samples, you can determine the enantiomeric excess by using the formula: EE = ([major concentration] - [minor concentration]) / total concentration. This essentially means that by assessing the concentrations and the specific rotations, we can identify which sample values give an EE of around 30%. It's also important to understand why knowing the specific rotation of a pure enantiomer is crucial in these calculations. Without this information, deducing the EE can be significantly more challenging, which could lead to substantial errors when answering exam queries. Additionally, familiarity with the use of polarimeters in measuring specific rotation can also enhance your practical skills in laboratories. Remember, consistent practice and familiarity with such calculations can greatly reduce the uncertainties and enhance confidence during examinations in organic chemistry.