Unsaturated hydrocarbons (alkenes)

Lekture 2

Методы мониторинга

Виды мониторинга

1. Какие объекты на земной поверхности могут представлять интерес для экологического мониторинга?
2. Виды объектов мониторинга в земной коре.
3. Название мониторинга, когда объектом рассматривается человек.
4. Что такое компоненты природной среды?
5. Локальный мониторинг к какому виду мониторинга относится?
6. Что понимается под национальным мониторингом?
7. Методы анализа образцов.
8. Чем отличается химический мониторинг от физического?
9. Привести пример импактного мониторинга.

1. Чем отличаются контактные методы мониторинга от дистанционных?
2. Перечислите устройства дистанционного мониторинга.
3. Что такое лидары?
4. Приведите примеры химических и физических методов мониторинга.
5. Чем отличается биоиндикация от биотестирования?

Lek:Alimkulova E. J.

Unsaturated hydrocarbons are alkenes. They all contain only one carbon-to-carbom double bond (C=C). Because of the double bond, the molecule contains two fewer hydrogen atoms than the corresponding alkane. It is not completely “saturated” with hydrogen, as the alkanes are. The IUPAC names for alkenes always end in “-ene”. The general molecular formula for members of the alkene series is C_nH_2n. The first representative of the alkene is ethylene-C₂H₄, next-propylene - C₃H₆.

H₂C=CH₂

IUPAC name ethane

Common name ethylene

Like all hydrocarbons, alkenes are insoluble in water< though soluble in nonpolar organic solvents. Their densities are less than of water.

The carbon-to-carbon double bond is the reactive center of an alkene/ Alkenes undergo addition reactions in which atoms or group of atoms add to the double bond and, in doing so, saturate the bond. The addition of hydrogen to an alkene or alkyne is called hydrogenation. Frequently a catalyst such as finaly divided nickel metal is required to facilitate the addition. Hydrogen may be under high pressure.

Ni

CH₂=CH₂ + H₂(g) → CH₃-CH₃

Heat, pressure

Ethene Ethane

When a halogen. such as bromine, adds to an alkene. In saturates the bond, adding one bromine atom to each carbon.

CH₃-CH=CH-CH₂ + Br₂ → CH₃-CHBr –CHBr –CH₃

Propene (colorless) Bromine (red-brown) 1, 2- dibrompropane (colorless)

The addition of a halogen to an alkene occurs quickly at room temperature and, unlike the halogenation of saturated hydrocarbons, does not require ultraviolet light. The color change that accompanies the reaction makes a useful tool (инстумент) to determine if a compound unsaturated.

If an organic hydrocarbon quickly discharges the red-brouwn color o bromine when a few drops of Br₂ solution are added to it, then the compound must be an unsaturated hydrocarbon containing either a double bond (an alkene) or a triple bond (an alkyne) between to adjacent carbon atoms.

Another identifying test for alkenes is Baeyer Permanganate Test, in which the alkene is oxidized by dilute potassium permanganate, KMnO₄. The color change of the solution from purple to brown (or black) indicates the presence of an alkene or an alkyne.

│ │

── CH=CH─ + KMnO4 → ── C─C ─ + MnO₂ (s)

│ │ │ │

HO OH

Alkene Potassium a diol manganese (IY) oxide

(colorless) permanganate (colorless) (brown black)

Alkenes, like all hydrocarbons, combust to form carbon dioxide and water. In an open container (сосуд) alkenes burn with a luminouse yellow flame and produce some smoke and soot. The combustion of an alkene produces slightly less heat energy than the same mass of the corresponding alkane.

CH₂=CH₂ (g) + 3O₂ → 2 CO₂ (g) + 2 H₂O (g)

Next equation indicated to chemical reaction an ethene with water:

CH₂=CH₂ (g) + HOH → CH₂─CH₂OH

Ethene ethanol (alcohol)

Marcovnikov’s rule:

CH₂─CH=CH₂ + HCl → CH₃ ─CHCl─CH₃

1-propene 2-chlorpropane

Reaction of the polymerization:

CH₂=CH₂ (g) + CH₂=CH₂ + CH₂=CH₂ + … → (─CH₂ ─CH₂ ─)n

Ethene polyethylene (polimer)

Formation of alkenes- reaction of the dehydrotation of alcohol:

H2SO4

CH₃─CH₂OH → CH₂=CH₂ (g) + HOH(liq)

ethanol (alcohol) ethane

Glossary:

Alkenes – Алкандар - Алкены

The alkenes are unsaturated hydrocarbons and they all contain only one

carbon-to-carbon double bond (C=C).

Ethene – этен – этен

ethanol (alcohol) - этанол (спирт) - этанол (алкоголь)

Carbohydrates – көмiрсутектер – углеводороды

References:

Frederick A. Bettelheim, Joseph M. Landesberg. Organic Chemistry

Charles H.Yenrickson, Larry C. Byrd, Norman W. Hunter. Organic Chemistry.

Cтепаненко Б.Н. Органическая химия.

Грандберг А.Г. Основы органической химии.

Ахметов А. Органикалык химия.

Elements of organic chemistry

KATU Technical Faculty

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