Ch. 6 - Stereoisomerism: Arrangement of Atoms in Space

Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition

Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook

Mullins 1st Edition

Ch. 6 - Stereoisomerism: Arrangement of Atoms in Space

Problem 26

Chapter 5, Problem 26

(R)-Limonene is a cyclic terpene responsible for the smell of oranges and other citrus fruits.
(a) Given that (R)-limonene rotates plane-polarized light in the clockwise direction, should it be referred to as (d) or (l)?
(b) Is it (+) or (-)?
(c) What direction (d or l; + or −) would you expect (S)-limonene to rotate plane-polarized light?

Verified step by step guidance

Step 1: Understand the relationship between the (R) and (S) stereochemical designations and the direction of rotation of plane-polarized light. The (R) and (S) designations are based on the Cahn-Ingold-Prelog priority rules and do not directly indicate the direction of optical rotation.

Step 2: Recall that the terms (d) and (l) refer to dextrorotatory and levorotatory, respectively. A compound is dextrorotatory (d) if it rotates plane-polarized light clockwise, and levorotatory (l) if it rotates plane-polarized light counterclockwise. Since (R)-limonene rotates light clockwise, it should be referred to as (d).

Step 3: Understand the relationship between the (+) and (−) notation and optical rotation. The (+) notation corresponds to clockwise rotation (dextrorotatory), while the (−) notation corresponds to counterclockwise rotation (levorotatory). Since (R)-limonene rotates light clockwise, it is also (+).

Step 4: Consider the stereochemical inversion from (R)-limonene to (S)-limonene. The (S)-enantiomer of a chiral compound typically rotates plane-polarized light in the opposite direction to its (R)-enantiomer. Therefore, if (R)-limonene is (d) and (+), (S)-limonene would be (l) and (−).

Step 5: Summarize the findings: (a) (R)-limonene is (d), (b) (R)-limonene is (+), and (c) (S)-limonene is expected to be (l) and (−), as it rotates plane-polarized light in the opposite direction to (R)-limonene.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Optical Activity

Optical activity refers to the ability of chiral compounds to rotate the plane of polarized light. This property arises from the asymmetry of the molecule, which can exist in two enantiomeric forms that rotate light in opposite directions. The direction of rotation is designated as clockwise (dextrorotatory, +) or counterclockwise (levorotatory, -). Understanding optical activity is crucial for distinguishing between enantiomers.

Enantiomers and Chirality

Enantiomers are pairs of molecules that are non-superimposable mirror images of each other, typically due to the presence of a chiral center. Chirality is a key concept in organic chemistry, as it affects the physical and chemical properties of compounds, including their interaction with polarized light. The designation of enantiomers as (R) or (S) is based on the Cahn-Ingold-Prelog priority rules, which help determine their spatial arrangement.

Cahn-Ingold-Prelog System

The Cahn-Ingold-Prelog (CIP) system is a set of rules used to assign the configuration of chiral centers in molecules. It involves ranking the substituents attached to the chiral carbon based on atomic number and connectivity. The configuration is designated as (R) for clockwise and (S) for counterclockwise arrangement when viewed from a specific perspective. This system is essential for accurately describing the stereochemistry of organic compounds.

Recommended video:

Guided course

01:48

Why stereoisomers need their own naming system.

Related Practice

Textbook Question

Naproxen is a commercially available anti-inflammatory sold under the name Aleve.

(a) Assign the absolute configuration as R or S.

views

Textbook Question

Based on the absolute configuration of (S)-butan-2-ol, what can you say about the direction it rotates plane-polarized light?

views

Textbook Question

Prioritize the substituents at each chiral center and then, by each of the two methods discussed in Section 6.3.2.4, determine the absolute configuration. [Do not use your models, except to check your answers.]

(d)

Textbook Question

Naproxen is a commercially available anti-inflammatory sold under the name Aleve.

(b) Given that naproxen rotates plane-polarized light in the clockwise direction, should it be referred to as (d) or (l)?

(d) What direction (d or l; + or −) would you expect the enantiomer of naproxen to rotate plane-polarized light?

(h)

(c)