光学回転に対する適合効果. 3-置換された1-ブテノース
Kenneth B Wiberg1, Patrick H Vaccaro, James R Cheeseman
1Department of Chemistry, Yale University, New Haven, Connecticut 067520-8107, USA. kenneth.wiberg@yale.edu
Journal of the American Chemical Society
|February 13, 2003
まとめ
この研究では,分子構成が (R) - (((-) -3) -クロロ-1-ブーテンの光学回転に大きく影響し,計算された値はトルション角度によって大きく異なることが明らかになりました. 観測された回転は予測されたより小さく,複雑な要因がこの現象に影響することを示唆しています.
科学分野:
- * オーガニック・ケミストリー
- * コンピューティング・ケミストリー
- * 立体化学について
背景:
- *ヒラリティと光学活動は,立体化学において極めて重要です.
- * 光学回転における構成効果を理解することは,分子特性を予測する上で鍵となる.
- * (R) -(-) -3-クロロ-1-ブテンは,これらの関係を研究するためのモデル化合物として機能します.
研究 の 目的:
- * (R) -(-) -3-クロロ-1-ブーテンの光学回転を計算および分析する.
- * C=C-C-Cのトルション角度が光学回転に及ぼす影響を調査する.
- * 理論的な計算と実験的観測を比較し,置換効果を探求する.
主な方法:
- * 光学回転の理論的な計算.
- * 扭転角度に基づく形状分析.
- * 形状均衡を分析するための温度依存研究.
- * 光学回転に対する置換効果 (F,CN,CCH) の理論的検討.
主要な成果:
- * 光学回転がC=C-C-Cのトルション角度に大きく依存することを計算した.
- *コンフォマー間の自由エネルギー差は1315cal/molで決定された.
- *観測された回転は,計算値より約2.6倍小さかった.
- * 光学回転に対する置換効果は最小であることが判明しました.
結論:
- *分子構成は,光学回転を決定する上で重要な役割を果たします.
- * 計算された回転と観測された回転の間の不一致は,洗練された理論モデルの必要性を強調する.
- * 代替物の電子効果が光学回転に及ぼす影響は,形状効果よりも少ない.
関連する概念動画
02:30Stability of Substituted Cyclohexanes
This lesson discusses the stability of substituted cyclohexanes with a focus on energies of various conformers and the effect of 1,3-diaxial interactions.
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...
02:37Disubstituted Cyclohexanes: cis-trans Isomerism
Depending upon the different spatial orientation of the substituents, the disubstituted cycloalkanes exhibit two types of stereoisomers. The cis isomers have the substituents on the same side of the ring, whereas the trans isomers have the substituents on the opposite sides. These stereoisomers exhibit different physical properties and cannot be interconverted without breaking the carbon-carbon bonds.
In cyclohexane, the substituents can occupy different positions generating distinct isomers.
In cyclohexane, the substituents can occupy different positions generating distinct isomers.
02:24Properties of Enantiomers and Optical Activity
It is essential to understand the difference between chiral and achiral interactions and the implications thereof in optical activity and their applications. Just as our feet, which are chiral, interact uniquely with chiral objects, such as a pair of shoes, but identically with achiral socks, enantiomers of a molecule exhibit different properties only when they interact with other chiral media. An example of a significant implication from this facet is the phenomenon known as optical activity,...
01:26Photochemical Electrocyclic Reactions: Stereochemistry
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
![[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2Ffiles%2Fmedia%2Fscience-education%2Fscience-education-thumbs%2F12422.jpg&w=3840&q=75)
01:21[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement
The Cope rearrangement is classified as a [3,3] sigmatropic shift in 1,5-dienes, leading to a more stable, isomeric 1,5-diene. The reaction involves a concerted movement of six electrons, four from two π bonds and two from a σ bond, via an energetically favorable chair-like transition state.
01:18Directing and Steric Effects in Disubstituted Benzene Derivatives
When disubstituted benzenes undergo electrophilic substitution, the product distribution depends on the directing effect of both substituents. When the directing effects of both substituents reinforce each other, a single product is obtained. For example, bromination of p-nitrotoluene occurs ortho to the methyl group and meta to the nitro group, which is the same position, resulting in a single product. However, if the directing effects of the two groups oppose each other, the more strongly...