Name: aromatic compounds in plants and fuels
Uploaded: 2023-04-30T10:30:40.000Z
Duration: 1 min 25 s
Channel: JoVE

방향족 화합물은 고리로 둘러싸인 공액 π 결합을 가진 탄화수소입니다. 벤젠 및 그 유도체는 방향족 화합물의 가장 잘 알려진 예입니다.
원래 벤젠 유도체는 식물과 나무에서 생산되는 천연 오일에서 분리되었으며 독특한 냄새 때문에 '방향족'이라고 불렸습니다.
예를 들어, 아몬드와 체리의 벤즈알데히드, 톨루 발삼의 톨루엔, 정향의 유제놀은 뚜렷한 냄새가 납니다.
시간이 지남에 따라 방향족이라는 용어는 향기가 나는지 여부에 관계없이 모든 벤젠 유도체를 계속 설명해 왔습니다. 예를 들어, 진통제인 아스피린에는 무취의 방향족 화합물인 아세틸살리실산이 함유되어 있습니다.
구조적으로 방향족 화합물은 불포화 탄화수소가 높으며 알켄, 알카인 및 개방 사슬 폴리엔과 다른 화학적 거동을 나타냅니다.
단순 방향족 화합물의 주요 공급원은 석탄, 타르 및 석유입니다.
콜타르의 분별 증류는 벤젠, 톨루엔, 자일렌, 나프탈렌 등과 같은 많은 방향족 화합물을 생성합니다.
마찬가지로, 석유 정제 과정에서 알칸은 방향족 화합물로 전환됩니다.

방향족 화합물: 개요

Aromatic Compounds: Overview

일반적으로 '방향족'이라는 용어는 신선한 꽃, 갓 준비한 커피 등에서 기분 좋은 냄새나 향기를 의미합니다. 유기화학의 초기 역사에서는 식물의 기분 좋은 냄새 오일에서 많은 벤젠 유도체가 추출되었습니다. 예를 들어, 바닐린은 바닐라 오일에서, 메틸 살리실레이트는 윈터그린 오일에서, 신남알데히드는 계피 오일에서 분리되었습니다. 이 모두는 기분 좋은 냄새를 풍겼습니다. 따라서 방향족이라는 이름이 주어졌습니다.

1825년에 패러데이는 압축 조명 가스(가스등에서 연소되는 연료)에서 벤젠을 분리하고 이를 "수소의 중탄화수소"라고 명명했습니다. 그는 또한 화합물의 원소 분석을 수행하여 수소와 탄소의 비율이 1:1임을 관찰했습니다.

나중에 아일하르트 미처리히는 1834년에 벤조산(벤조인 검에서 분리됨)과 산화칼슘으로부터 벤젠을 합성했습니다. 그는 증기 밀도 측정을 수행하여 벤젠의 분자식이 C_6H_6임을 보여주었습니다. 새로운 화합물은 벤조인 검에서 파생되었기 때문에 그는 그것을 벤진이라고 명명했으며, 현재는 벤젠으로 알려져 있습니다. 이는 실험실 용매로 사용됩니다.

<img alt="Figure1" src="/files/ftp_upload/12448/12448_PT_Figure_1.svg" style="text-align: center; height: 125px;">

'방향족'이라는 용어는 향이 있든 없든 모든 벤젠 유도체를 설명하는 데 여전히 사용됩니다. 천연 및 의약품 화합물의 대부분은 방향족입니다. 예를 들어 에스트론은 스테로이드, 아토르바스타틴(리피토)은 콜레스테롤 저하제, 졸로프트는 항우울제, 세레벤트는 천식 치료에 사용되는 방향족 화합물이다.

<img alt="Figure2" src="/files/ftp_upload/12448/12448_PT_Figure_2.svg" style="text-align: center; height: 425px;">

방향족 화합물은 주로 석탄과 석유에서 얻습니다. 석탄은 공기가 없는 상태에서 1000°C로 가열하면 콜타르를 생성합니다. 콜타르는 분별 증류 시 벤젠, 톨루엔, 디메틸벤젠(자일렌), 나프탈렌, 비페닐, 인덴, 안트라센 등과 같은 많은 방향족 탄화수소를 생성합니다.

그러나 방향족 화합물은 석유에서 직접 얻을 수 없습니다. 석유 정제 과정에서 알칸은 촉매 존재 하에 고압 하에서 500°C에서 방향족 화합물로 전환됩니다.

일반적으로 '아로마틱'이라는 용어는 신선한 꽃, 갓 준비한 커피 등에서 나오는 기분 좋은 냄새나 향기를 나타냅니다. 초기 역사에서 ...

Education

교육

JoVE Core

Organic Chemistry

유기 화학

Unit 1

제1단원

Aromatic Compounds

방향족 화합물

KEY TERMS AND CONCEPTS

주요 용어 및 개념

aromatic compounds in plants and fuels

Aromatic compounds are linked to both pleasant smells and important chemical structures. The word aromatic first came from fragrant natural sources such as fresh flowers and spices. Early organic chemists isolated benzene derivatives from oils of plants, including vanillin from vanilla, methyl salicylate from wintergreen, and cinnamaldehyde from cinnamon.

The history of benzene also helped shape the idea of aromatic compounds. In 1825, Faraday isolated benzene from compressed illuminating gas, which was used in gaslights. He called it bicarburet of hydrogen and found a 1:1 ratio of hydrogen to carbon. In 1834, Eilhardt Mitscherlich made benzene from benzoic acid, which comes from gum benzoin, and calcium oxide. He used vapor density measurements to show that benzene has the formula C6H6, and he named it Benzin, now called benzene.

Today, the term aromatic includes many benzene derivatives, even when they do not smell pleasant. Benzene itself is used as a laboratory solvent. Many natural and pharmaceutical compounds are aromatic, including estrone, atorvastatin (Lipitor), Zoloft, and Serevent.

Aromatic compounds are mainly obtained from coal and petroleum. When coal is heated to 1000 °C without air, it forms coal tar. Fractional distillation of coal tar gives aromatic hydrocarbons such as benzene, toluene, xylene, naphthalene, biphenyl, indene, and anthracene. Aromatic compounds are not taken directly from petroleum, but petroleum refining can convert alkanes into aromatic compounds with a catalyst at 500 °C under high pressure.

Aromatic Compounds in Plants and Fuels

aromatic compounds: overview

Aromatic compounds are linked to both pleasant smells and important chemical structures. The word aromatic first came from fragrant natural sources such as fresh flowers and spices. Early organic chemists isolated benzene derivatives from oils of plants, including vanillin from vanilla, methyl salicylate from wintergreen, and cinnamaldehyde from cinnamon. The history of benzene also helped shape the idea of aromatic compounds. In 1825, Faraday isolated benzene from compressed illuminating gas,...

nomenclature of aromatic compounds with a single substituent

nomenclature-of-aromatic-compounds-with-a-single-substituent

Naming Benzene Derivatives with One Group

Benzene derivatives with one substituent are named by attaching the substituent name to benzene. Benzene is the simplest aromatic hydrocarbon, also called an arene. For simple monosubstituted benzene compounds, IUPAC naming uses the group name as a prefix. Halogen-substituted benzene compounds follow this pattern. The halogen prefix can be fluoro, chloro, bromo, or iodo. When an alkyl group is attached to the benzene ring, the name depends on the chain length of that group. If the alkyl chain...

nomenclature of aromatic compounds with multiple substituents

nomenclature-of-aromatic-compounds-with-multiple-substituents

Naming Benzene Rings with Multiple Groups

Naming benzene rings with multiple groups depends on how many substituents are attached. For benzene derivatives with two groups, three constitutional isomers are possible. The position of each group is described with IUPAC naming rules. For disubstituted benzene compounds, the relative positions can be shown with ortho, meta, and para. These terms are also written as o, m, and p. They can also be written with numbers, such as 1,2- for ortho, 1,3- for meta, and 1,4- for para. Dimethyl benzene,...

structure of benzene: kekul&eacute; model

Kekule’s Benzene Model and Its Limits

Kekule’s benzene model describes benzene as a six-carbon ring with alternating pi bonds. August Kekule proposed this structure in 1865 from the formula C6H6, the idea that all benzene hydrogens are equivalent, and the rule that each carbon has four bonds because of tetravalency. In this model, each carbon is attached to one hydrogen atom. It also predicts two isomers for 1,2-disubstituted benzene derivatives. In one form, the substituted carbons are linked by a double bond, and in the other...

structure of benzene: molecular orbital model

structure-of-benzene-molecular-orbital-model

Benzene π Orbitals and Electron Delocalization

Benzene has a planar ring structure with delocalized π electrons. Its six carbon atoms form a regular hexagon, and each carbon is sp2 hybridized. The C–C–C and H–C–C bond angles are 120°, which matches the flat shape of the ring. Each carbon is bonded to three other atoms. The C–H bond length is 109 pm, and the C–C bond length is 139 pm. That C–C distance is midway between the single bond length of sp3 hybridized carbons, 154 pm, and the sp2 value, 133 pm. Beneath and above the ring plane,...

criteria for aromaticity and the h&uuml;ckel 4n + 2 rule

criteria-for-aromaticity-and-the-hckel-4n-2-rule

H&uuml;ckel Rule and Aromatic Ring Criteria

Aromatic rings follow H&amp;uuml;ckel’s rule, also called the 4n + 2 rule. This rule helps identify which unsaturated cyclic compounds are aromatic and why some ring systems are unstable instead. Benzene is the classic example, while cyclobutadiene and cyclooctatetraene show different behavior and are not aromatic. Eric H&amp;uuml;ckel, a German chemical physicist, first described the structural features needed for aromaticity. An aromatic compound must be cyclic, planar, and continuously...

h&uuml;ckel's rule diagram of &pi; mos: frost circle

Frost Circle for Pi Orbital Energies

The Frost circle is a graphical method for showing the relative energies of pi molecular orbitals in planar, fully conjugated, monocyclic compounds. It is also called the inscribed polygon method. A. A. Frost and Boris Musulin first described this method in 1953. To build a Frost circle, draw a polygon with the same number of edges as the number of carbons in the cyclic system. Place one vertex pointing downward. Then draw a circle around the polygon so that every vertex touches the circle.

frost circles for different conjugated systems

frost-circles-for-different-conjugated-systems

Using Frost Circles to Test Aromaticity

Frost circles help test whether a cyclic compound is aromatic by using the inscribed polygon method and Hückel’s 4n + 2 rule. A compound is stable and aromatic when every bonding molecular orbital (MO) is completely filled with a pair of electrons. If electrons occupy non-bonding or antibonding orbitals, the compound is unstable and not aromatic. Frost circle diagrams for cycloalkenes with 4 to 8 carbons show a clear pattern. The number of bonding MOs is always odd. The electrons needed to...

aromatic hydrocarbon anions: structural overview

aromatic-hydrocarbon-anions-structural-overview

Cyclopentadienyl Anion and Aromaticity

Cyclopentadiene is a neutral hydrocarbon that is not aromatic. It contains an odd number of carbon atoms and one CH2 group in the ring. With only 4 pi electrons, it does not follow the 4n + 2 pi electron rule. The CH2 carbon is sp3 hybridized, so it has no vacant p orbital to keep p orbitals overlapped around the ring. That break in overlap stops pi electrons from spreading across the entire ring. As a result, cyclopentadiene does not meet the usual aromaticity criteria. If one hydrogen is...

aromatic hydrocarbon cations: structural overview

aromatic-hydrocarbon-cations-structural-overview

Cycloheptatrienyl Cation and Aromaticity

Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon with seven carbon atoms. One carbon in the ring is sp3 hybridized, which breaks the continuous overlap of p orbitals. Even though the ring has three double bonds and 6 π electrons, cycloheptatriene is not aromatic because the p orbitals do not form one uninterrupted loop. Removing one hydrogen from the CH2 group changes the ring. If that hydrogen is removed with both, one, or no electrons, the products are the cycloheptatrienyl...

five-membered heterocyclic aromatic compounds: overview

five-membered-heterocyclic-aromatic-compounds-overview

Five-Membered Aromatic Rings with Heteroatoms

Five-membered aromatic rings with heteroatoms are cyclic compounds that contain one or more atoms other than carbon in the ring. They are aromatic and can have either five or six atoms in the ring. Common examples include pyrrole, furan, thiophene, and imidazole. These rings differ by the heteroatom present. Pyrrole has one nitrogen atom with one lone pair of electrons. Furan has one oxygen atom, and thiophene has one sulfur atom. Both furan and thiophene have two lone pairs of electrons.

nmr spectroscopy of aromatic compounds

Aromatic Ring Shifts in NMR Spectra

Aromatic ring shifts in NMR spectra help identify aromatic compounds using proton NMR and carbon-13 NMR. Aromatic hydrogens are often strongly deshielded by the aromatic ring current, so they usually appear in the 6.5–8.0 ppm range in proton NMR. In benzene, the hydrogens directly bonded to the ring absorb at 7.3 ppm. Larger aromatic rings can place hydrogens outside the usual range. In [18]annulene, the 12 outer hydrogens are highly deshielded by the ring current and absorb downfield at 9.3...

key terms and concepts

Explore how aromatic compounds were first found in plant oils, how benzene was identified, and how coal tar and petroleum produce key aromatic hydrocarbons.

Aromatic Compounds in Plants and Fuels | JoVE K12

organic chemistry

JoVE Core Organic Chemistry explains basic concepts of stereochemistry, reactions, and mechanisms using concise and easy-to-understand animated video lessons. Additionally, the scientist-in-action videos demonstrate the application of related concepts in classical and original research experiments performed in today's laboratories worldwide.

Aromatic Compounds in Plants and Fuels

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