Hexahelicene seems a poor candidate for optical activity because all its carbon atoms are sp2 hybrids and presumably flat. Nevertheless, hexahelicene has been synthesized and separated into enantiomers. Its optical rotation is enormous: [α]D = 3700°. Explain why hexahelicene is optically active, and speculate as to why the rotation is so large.
Ch. 16 - Aromatic Compounds
16장, 문제 50
Chlorophyll is the general name for a family of compounds present in algae and green plants. These molecules use the energy in sunlight to convert carbon dioxide and water into carbohydrates and other energy sources. At the heart of chlorophyll (shown below) is a large-ring magnesium complex called a chlorin. Circle each double bond in the large cyclic conjugated pi system that makes it aromatic. How many pi electrons are in this aromatic system?

검증된 단계별 안내1
Step 1: Identify the large cyclic conjugated pi system in the chlorin ring structure. This is the central ring system containing magnesium (Mg) and nitrogen atoms, along with alternating double bonds.
Step 2: Circle each double bond in the cyclic conjugated pi system. Look for alternating single and double bonds within the ring structure, which contribute to conjugation and aromaticity.
Step 3: Count the number of pi electrons in the conjugated system. Each double bond contributes 2 pi electrons, and lone pairs on nitrogen atoms may also contribute if they are part of the conjugated system.
Step 4: Apply Hückel's rule for aromaticity, which states that a molecule is aromatic if it has (4n + 2) pi electrons, where n is a non-negative integer. Verify if the total number of pi electrons satisfies this rule.
Step 5: Confirm the aromaticity of the chlorin ring system based on the conjugated pi electron count and Hückel's rule. This will determine if the system is aromatic.

비슷한 문제에 대한 검증된 영상 답변:
이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.
영상 길이:
5m주요 개념
질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.
Aromaticity
Aromaticity refers to a property of cyclic compounds that exhibit enhanced stability due to the delocalization of pi electrons across the ring structure. For a compound to be considered aromatic, it must follow Hückel's rule, which states that it should have a planar structure and contain a specific number of pi electrons (4n + 2, where n is a non-negative integer). This concept is crucial for understanding the stability and reactivity of compounds like chlorophyll.
추천 영상:
Intro to Aromaticity
Conjugated Pi System
A conjugated pi system consists of alternating single and double bonds, allowing for the overlap of p orbitals and the delocalization of electrons. In chlorophyll, the conjugated system contributes to its aromatic character and plays a significant role in its ability to absorb light. Identifying the double bonds in this system is essential for determining the number of pi electrons involved.
추천 영상:
Definition of Conjugation
Pi Electrons
Pi electrons are the electrons found in the pi bonds of a molecule, which are formed by the sideways overlap of p orbitals. In the context of aromatic compounds, the count of pi electrons is critical for assessing aromaticity. In chlorophyll, counting the pi electrons in the cyclic conjugated system will help determine its stability and reactivity, as well as its role in photosynthesis.
추천 영상:
Counting pi electrons
관련 실천
교과서 질문
747
views
교과서 질문
An unknown compound gives the following mass, IR, and NMR spectra. Propose a structure, and show how it is consistent with the spectra. Show the fragmentations that give the prominent peaks at m/z 127 and 155 in the mass spectrum.
<IMAGES>
3377
views
교과서 질문
Consider the following compound, which has been synthesized and characterized:
a. Assuming this molecule is entirely conjugated, do you expect it to be aromatic, antiaromatic, or nonaromatic?
b. Why was this molecule synthesized with three tert-butyl substituents? Why not make the unsubstituted compound and study it instead?
818
views
