Question

1. Дайте сравнительную характеристику бензола и любого предельного углеводорода по плану: а) состав; б) структурная формула; в) химические свойства бензола, отличающие его от предельных углеводородов и общие с ними. Запишите уравнения необходимых химических реакций.

Answer 1

А)Возьмём предельный углеводород - метан (он же простейший представитель алканов). Его молекула содержит только простые сигма-связи. Молекула метана имеет тетраэдрическое строение с валентным углом Н-С-Н равным 109°28'. Формула метана - СН4 (1 атом углерода и 4 атома водорода). Структура метана:
Н
|
H -C-H
|
H
Бензол - ароматический циклический углеводород, имеет π-комплекс. Формула С6Н6.
Б)
Сходство с предельными (алканами) заключается в реакциях горения (получаются углек. газ и вода):
СН4 + 2О2 = СО2 + 2Н2О + 890 кДж
2С6Н6 + 15О2 = 12СО2 + 6Н2О.
Реакция галогенирования у бензола и метана различаются. У метана под действием света происходит полное замещение атомов водорода на хлор, образуется тетрахлорметан : ССl4. В случае брома у бензола: С6Н6 + Br2 = C6H5Br (бромбензол) + HBr
А при присоединении хлора образуется гексахлорциклогексан (реакцию не помню)
Ещё для бензола и алканов характерно нитрование : С6Н6 + НNO3 = C6H5NO2 + H20 (образ. нитробензол).
Алканы: СН4 + НNO3 = CH3NO2 (нитрометан) + Н2О
Ещё характерно гидрирование (только для бензола): бензол + 3Н2 = С6Н12 (правильный шестиугольник и вещество - циклогексан).
Вроде все. Вообще различия объясняются строением алканов и бензола. У алканов все связи одинарные, а у бензола пи-комплекс. + бензол ядовит

Answer 2

Comparative Characteristics of Benzene and a Saturated Hydrocarbon:

a) Composition: - Benzene: Benzene is an aromatic hydrocarbon composed of six carbon atoms and six hydrogen atoms. Its molecular formula is C6H6. - Saturated Hydrocarbon: A saturated hydrocarbon is a hydrocarbon compound that contains only single bonds between carbon atoms. The number of hydrogen atoms in a saturated hydrocarbon is determined by the formula CnH2n+2, where n represents the number of carbon atoms.

b) Structural Formula: - Benzene: The structural formula of benzene consists of a hexagonal ring of six carbon atoms, with alternating single and double bonds. Each carbon atom is bonded to one hydrogen atom. - Saturated Hydrocarbon: The structural formula of a saturated hydrocarbon depends on the specific compound. For example, the structural formula of methane (CH4), the simplest saturated hydrocarbon, consists of a single carbon atom bonded to four hydrogen atoms.

c) Chemical Properties that Distinguish Benzene from Saturated Hydrocarbons and Common Properties: - Benzene: - Aromaticity: Benzene exhibits aromaticity, which is a property of certain compounds with a cyclic structure and a delocalized system of π electrons. This property gives benzene its unique stability and reactivity. - Electrophilic Substitution: Benzene undergoes electrophilic substitution reactions, where an electrophile replaces one of the hydrogen atoms on the benzene ring. This is due to the delocalized π electron system, which stabilizes the intermediate carbocation formed during the reaction. - Resonance Stabilization: Benzene's delocalized π electron system allows for resonance stabilization, which contributes to its stability and reactivity. - Saturated Hydrocarbons: - Lack of Aromaticity: Saturated hydrocarbons do not exhibit aromaticity because they do not have a delocalized π electron system. - Lack of Electrophilic Substitution: Saturated hydrocarbons do not undergo electrophilic substitution reactions because they do not have a reactive π electron system. - Lack of Resonance Stabilization: Saturated hydrocarbons do not have a delocalized π electron system, so they do not exhibit resonance stabilization.

Chemical Reactions:

Here are some necessary chemical reactions involving benzene and a saturated hydrocarbon:

1. Benzene Reactions: - Nitration of Benzene: Benzene reacts with nitric acid in the presence of sulfuric acid to form nitrobenzene. This reaction is an example of electrophilic substitution. ``` C6H6 + HNO3 -> C6H5NO2 + H2O ``` - Halogenation of Benzene: Benzene reacts with halogens (e.g., chlorine or bromine) in the presence of a catalyst (e.g., iron or aluminum chloride) to form a halogenated benzene compound. This reaction is also an example of electrophilic substitution. ``` C6H6 + Br2 -> C6H5Br + HBr ```

2. Saturated Hydrocarbon Reaction: - Combustion of Methane: Methane, a saturated hydrocarbon, reacts with oxygen to produce carbon dioxide and water vapor. This reaction is an example of complete combustion. ``` CH4 + 2O2 -> CO2 + 2H2O ```

Please note that these are just a few examples of chemical reactions involving benzene and a saturated hydrocarbon. There are many more reactions that can occur with these compounds, depending on the specific conditions and reactants involved.