METHANE

Methane

- First in the series of Parrafin/Alkane (which is saturated)
- The simplest alkane and the primary component of natural gas.
- colorless/ odorless
- abundant hydrocarbon is a greenhouse gas, contributing to climate change

Water Displacement

Methane is insoluble in water and hence is conveniently collected by?

Alkaline KMnO₄
Bases
Acids
Alcoholic iodine

Methane is inert toward the common laboratory reagents such as?

90%

Natural gas contains approximately ____ methane; hence its synthesis is significant.

Marsh Gas
Natural Gas

Methane is often referred as?

Anhydrous Barium Hydroxide

may be used instead of soda lime. Methane prepared in this manner contains certain impurities.

CH4 + Na2CO3 + H2O

Synthesis of Methane
CH3COONa + CaO + NaOH →

Decomposition Reaction

type of chemical reaction in which a single compound breaks down into two or more simpler substances. This process occurs when the original compound is subjected to heat, light, electricity, or other forms of energy.

C₂H₃NaO₂

Chemical Structure of Anhydrous Sodium Acetate

Anhydrous Sodium Acetate

- Serves as the source of acetate ions (CH3COO-) in the reaction.
- Sodium salt form of acetic acid (vinegar)/ the ethanoate ion
- It's written as NaCH3COO or NaC2H3O2

heated

When ______, anhydrous sodium acetate decomposes to release acetate ions, which subsequently react with the components of soda lime to produce methane.

Soda Lime

a mixture of sodium hydroxide (NaOH) and calcium oxide (CaO), acts as a strong base and dehydrating agent in the reaction.

Sodium Carbonate (Na2CO3)
Water Vapor (H2O)

The sodium hydroxide component of soda lime reacts with anhydrous sodium acetate to form?

Calcium Oxide

What component helps in the dehydration of the reaction mixture, facilitating the elimination of water molecules

Soda Lime

It promotes the decomposition of anhydrous sodium acetate and facilitates the formation of methane gas.

Dry Ignition Tube
Burner
Reagents

Set Up of Synthesis of Methane

Dry Ignition Tube

Is a glass tube typically made of borosilicate glass, resistant to high temperatures. It provides a controlled environment for the chemical reaction to occur. The tube is dry to prevent any moisture from interfering with the reaction.

Reaction with Bromine
Reaction with Alcoholic Iodine
Reaction with Alkaline KMnO4

Tests for Unsaturation

Reaction with Bromine

The decolorization of bromine water indicates the absence of unsaturation in methane. Any persistence of color suggests the presence of unsaturated hydrocarbons as impurities.

Reaction with Bromine

What is this?

Reaction to Alcoholic Iodine

What is this?

No Reaction
Alkanes do not react with Oxidizing Agents

Reaction to KMnO4

Combustion of Methane

Produces a clean, blue flame, indicating complete combustion to carbon dioxide and water. Any deviation from this observation may suggest impurities affecting the combustion process.

CO2 + 2H2O

Combustion Reaction of Methane
CH4 + 2O2 →

- Any discrepancies observed in the chemical tests could be attributed to impurities present in the synthesized methane. Common impurities may include ethylene, ethane, or other hydrocarbons with unsaturated bonds.
- The presence of impurities can affect the physical and chemical properties of methane, such as its reactivity with bromine and alkaline KMnO₄.
- Further purification techniques, such as fractional distillation or gas chromatography, may be required to isolate pure methane for specific applications.

Discussion of Combustion Reaction of Methane

Fourier Transform Infrared (FTIR)

- The preferred method of infrared spectroscopy.
- Determines the chemical bond between molecules/ bonding

Nuclear Magnetic Resonance (NMR)

- Use of Protons and determine the skeleton structure of the compound.
Ex: MRI (its function is like magnets)

Chromatography

Determines the compound based on its polarity

Test of Unsaturation

Determines if one carbon group is filled with hydrogen or not.

Instrumental Method

Best method to determine function group.

Recorded from 5000 to 400 cm−1 (2.0 to 25 μm), with special attention being given to the molecule's ν4 region (1300 cm−1, 7.69 μm) and the near-IR features at 4600 - 4100 cm–1 (2.17 - 2.44 μm)

Methane's IR spectra

Alcohols

- Organic compounds containing hydroxyl (-OH) functional groups attached to :
- saturated C atom of a simple alkyl group

Primary Alcohol

OH group attached to a primary carbon atom
Ex: Ethanol

Secondary Alcohol

OH group attached to a secondary carbon atom
Ex: 2- Propanol

Tertiary Alcohol

OH group attached to a tertiary carbon atom
Ex: 2-methy-2-propanol

Aliphatic alcohols and lower aromatic alcohols
Highly branched alcohols and alcohols with twelve or more carbon atoms (solid at room temperature & fruity odors)

Physical state of alcohols

Polar

Alcohols are _____ compounds

Dipole-dipole Interaction

The attraction between the positive end of one dipole and the negative end of the other.

greater than

Boiling points of alcohols are higher _________ alkanes and chloroalkanes of similar relative molecular mass

Boiling Point

Is the state of the internal pressure of hydrogen bond and surface pressure is equal.

- Alcohols with short carbon chains dissolve in water
- Solubility decreases sharply with the increasing length of the carbon chain
- Higher alcohols are insoluble in water
- Polyhydroxy alcohols are more soluble than monohydroxy
- Branched hydrocarbon increases the solubility of alcohol in water

Solubility of Alcohols in Water

In aqueous solution, alcohol will donated its proton to water molecule to give an alkoxide ion

Acidity of Alcohols

- Ethanol-solvent for varnishes, perfumes and flavorings, a medium for chemical reactions and in recrystallization
- Hypnotic (More chlorine causes depression)

Importance of Alcohols

- Grignard synthesis (more efficient because it can yield higher percentage of alcohols )
- Hydrolysis of alkyl halides
- Industrial and laboratory preparations

Preparation of Alcohol

Grignard reagents

are chemical compounds with the general formula R−Mg−X, where X is a halogen and R is an organic group, normally an alkyl or aryl.
(The reaction will never happen if there is a presence of water)

Alcoholic Fermentation

- A process of using yeasts (fungi) to convert sugars into alcohol.
- May be classified as oxidation, reduction, cleavage and combination reaction, which are promoted or catalyzed by enzyme.

zymase

ALCOHOLIC FERMENTATION
The enzyme known as ________, which yeast cells produce has the property of promoting the splitting of glucose by alcoholic fermentation with formation of ethyl alcohol and carbon dioxide

invertase

C12H22O11 + H2O
C6H12O6

zymase

C6H12O6
2CH3-CH2OH + 2CO2

Only the primary and secondary alcohols are oxidized by hot acidified potassium permanganate or potassium dichromate
1◦ or 2◦
- The purple color of potassium permanganate
- The potassium dichromate changes from orange to green

Oxidation of Alcohols

Tertiary Alcohol

Lucas Test
-immediate cloudiness

Secondary Alcohol

Lucas Test
-solution turns cloudy within about 5 minutes

Primary Alcohol

Lucas Test
- no cloudiness at room temperature

Iodoform Test

Ethanol and secondary alcohols containing the methyl alcohol group which react with alkaline solutions of iodine to form triiodomethane.

Phenols

Compounds that have –OH group attached directly to a benzene ring

- Colorless, crystalline, poisonous solid with phenolic odor
- Melting point 41C and Boiling Point 182C
-Sparingly soluble in water forming pink solution at room temperature
- Completely soluble above 68.50C
- Causes blisters on skin
- Used as disinfectants and in washrooms

Physical Properties of Phenols

- Phenols are more acidic than alcohol
- Basic Properties
- Test for the hydroxyl group
- Bromination of phenol

Properties of Phenols