Questions and Answers
What was the principal factor determining the migration of individual components in the chromatography of the reaction mixture?
What assumption is being made if scientists conclude that aspartic acid was formed by the prebiological synthesis?
What is the approximate Rf value of aspartic acid if aspartic acid = 2 and solvent front = 10?
Which of the following statements does NOT correctly describe the dehydration of malic acid to fumaric acid and maleic acid?
Signup and view all the answers
What type of functional group is formed when aspartic acid reacts with another amino acid to form a peptide bond?
Signup and view all the answers
If 2-pentanol replaces 1-pentanol in the reaction (SN2), why is the rate of substitution less?
Signup and view all the answers
If a solution containing certain compounds is injected into a gas-liquid chromatograph, which compound would be expected to produce the first peak?
Signup and view all the answers
What is the notation used for R vs. S stereochemistry?
Signup and view all the answers
In determining which reactant loses the -OH group when acetic acid and ethanol react to form an ester, which isotopic substitution would be most useful?
Signup and view all the answers
Study Notes
Chromatography and Migration
- Chromatography utilizes cellulose as a stationary phase, with water absorption critical for component migration.
- Principal migration factor is hydrogen bonding, influencing how strongly individual components adhere to the stationary phase.
Prebiological Synthesis Assumptions
- Aspartic acid formation presupposes the availability of Compound A and cyanide on primitive Earth.
- Important to consider starting materials when evaluating experimental relevance to primordial conditions.
Rf Value Calculation
- Rf value (retention factor) is a ratio of the distance traveled by the compound to the distance traveled by the solvent front.
- For aspartic acid, Rf calculation: travelled distance (2) / solvent front distance (10) = 0.20.
Dehydration Reactions
- Dehydration from malic acid yields fumaric and maleic acids, involving water molecule loss.
- This reaction is not stereospecific due to the formation of two distinct acid products.
Functional Groups in Peptide Bond Formation
- The reaction between aspartic acid and another amino acid generates an amide group during peptide bond formation.
Substitution Reactions and Steric Hindrance
- Substitution rate in nucleophilic reactions, such as replacing 1-pentanol with 2-pentanol, decreases due to increased steric hindrance at the 2-position.
- Steric hindrance impacts collision rates between nucleophiles and electrophiles, affecting reaction kinetics.
Gas-Liquid Chromatography Peaks
- In gas-liquid chromatography, methyl-2-butene is the first peak due to its lower molecular weight and weak intermolecular attractions, allowing it to migrate faster.
Stereochemistry Notation
- R and S configurations in stereochemistry denote optical isomers based on the arrangement of substituents around a chiral center.
- R configuration indicates a clockwise arrangement, while S indicates counter-clockwise.
Isotopic Substitution in Ester Reactions
- In ester formation from acetic acid and ethanol, replacing the hydroxyl oxygen of ethanol with O-18 is beneficial for tracking the -OH group loss.
- Isotopic labeling assists in tracing reaction mechanisms and understanding molecular transformations.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Prepare for the MCAT with our first practice exam flashcards. This quiz focuses on key concepts related to chromatography and the factors affecting component migration. Test your knowledge and boost your confidence before the big day.
