Organic Chemistry Flashcards

HYDROCARBONS

Experiment 12

CLASSIFICATION OF HYDROCARBONS

Hydrocarbons are organic compounds that primarily consist of carbon and hydrogen atoms. They are the fundamental building blocks of many other organic compounds and are mainly derived from crude oil and natural gas. Hydrocarbons are classified into two major categories:

1. Acyclic or open-chain hydrocarbons (also known as aliphatic hydrocarbons)

2. Cyclic or closed-chain hydrocarbons

Acyclic hydrocarbons are further divided into:

• Saturated hydrocarbons (Alkanes)

• Unsaturated hydrocarbons (Alkenes, Alkynes)

Cyclic hydrocarbons are divided into:

• Alicyclic hydrocarbons (Cycloalkanes, Cycloalkenes, Cycloalkynes)

  • Saturated (Cycloalkane)

  • Unsaturated (Cycloalkene, Cycloalkyne)

• Aromatic hydrocarbons

Details on Hydrocarbon Types:

• Alkanes: These are saturated hydrocarbons with single bonds only. They are relatively unreactive and undergo substitution reactions.

  • Example: Methane (CH4), Ethane (C2H_6)

• Alkenes: These are unsaturated hydrocarbons containing at least one carbon-carbon double bond. They are more reactive than alkanes and undergo addition reactions.

  • Example: Ethene (C2H4)

• Alkynes: These are unsaturated hydrocarbons containing at least one carbon-carbon triple bond. They are highly reactive and undergo addition reactions readily.

  • Example: Ethyne (C2H2)

• Cycloalkanes: These are saturated cyclic hydrocarbons. They have similar properties to alkanes but in a cyclic form.

  • Example: Cyclohexane (C6H{12})

• Cycloalkenes: These are unsaturated cyclic hydrocarbons containing at least one carbon-carbon double bond in the ring.

  • Example: Cyclohexene (C6H{10})

• Aromatic Hydrocarbons: These contain a benzene ring and exhibit unique properties due to the delocalization of electrons. They undergo electrophilic aromatic substitution reactions.

  • Example: Benzene (C6H6)

EXPERIMENTAL RESULTS

1. Ignition Test:

   • Benzene: Smoky luminous flame with soot formation

   • n-hexane: Not smoky; luminous flame with slight soot formation

   • Cyclohexane: Smoky luminous flame with soot formation, but not as much as benzene

   • Gasoline: Non-luminous flame with little or no soot formation

2. Test for Unsaturation (using KMnO4):

   • Benzene: Violet color of KMnO_4 remains the same

   • n-hexane: Violet color of KMnO_4 remains the same

   • Cyclohexane: Violet color of KMnO_4 remains the same

   • Gasoline: Violet color of KMnO_4 changed to brown

CHEMICAL REACTIONS

1. Equations for the complete combustion of a hydrocarbon:

   • When a hydrocarbon molecule burns in excess oxygen, the products are carbon dioxide and water.

   • General equation: hydrocarbon + oxygen → carbon dioxide + water

   • Example 1: CH4(g) + 2O2(g) \rightarrow CO2(g) + 2H2O(l)

   • Example 2: C2H4 + 3O2 \rightarrow 2CO2 + 2H_2O

   • Heavier hydrocarbons (more carbon atoms) don't evaporate as easily, making them less easy to combust.

   • Alkynes, aromatics, cycloalkanes, and cycloalkenes burn with sooty flames.

   • Examples:

     • Ethyne (acetylene) - alkyne, open chain

     • Benzene - aromatic, closed chain

     • Cyclohexene - cyclic, closed chain

     • Methane - alkane, open chain

Combustion Details:

• Complete Combustion: Requires an excess of oxygen to produce carbon dioxide and water. This results in a clean, blue flame.

• Incomplete Combustion: Occurs when oxygen is limited, producing carbon monoxide (toxic), soot (carbon particles), and water. This results in a smoky, yellow flame.

1. BAEYER TEST

   • Baeyer Test for Multiple Bonds (Potassium Permanganate Solution)

   • Tests for the presence of alkenes and alkynes

   • Alkene reaction: Alkene + KMnO4 + H2O \rightarrow Diol + MnO_2

   • Alkyne reaction: Alkyne + KMnO4 + H2O \rightarrow Tetraol + MnO_2

   • The purple color of the KMnO4 solution disappears, and a brown solid (MnO2) is formed.

CHEMICAL REACTIONS

1. Saturated hydrocarbons like alkanes and cycloalkanes undergo substitution reactions under rigorous conditions and are less reactive than unsaturated hydrocarbons (alkenes and alkynes).

2. Alkenes and alkynes undergo addition reactions.

3. Aromatic compounds like benzene undergo electrophilic aromatic substitution.

Reaction Types Explained:

• Substitution Reactions: Involve the replacement of one atom or group of atoms with another.

  • Example: Halogenation of alkanes

• Addition Reactions: Involve the addition of atoms or groups of atoms to a molecule, typically at a double or triple bond.

  • Example: Hydrogenation of alkenes

• Electrophilic Aromatic Substitution: Involve the substitution of an atom on an aromatic ring by an electrophile.

  • Example: Nitration of benzene

ALCOHOLS

Experiment 13

USES OF ALCOHOLS

• Starter

• Perfume

• Solvent

• Drinks

• Antiseptic

• Fuel

ALCOHOLS (R-OH)

Organic compounds containing the -OH (hydroxyl) functional group attached to a hydrocarbon skeleton (alkyl or aryl).

Classification based on the number of -OH groups:

• Monohydric (e.g., methanol)

• Diol (e.g., ethylene glycol)

• Triol (e.g., glycerol)

ALCOHOLS - EXAMPLES AND CLASSIFICATIONS

• Methanol (CH_3OH) (methyl alcohol)

• Ethanol (CH3CH2OH) (ethyl alcohol)

• Phenol (C6H5OH)

• Ethylene glycol (HOCH2CH2OH)

• 2-Propanol (isopropyl alcohol) (CH3CH(OH)CH3)

• Primary (1^\circ), secondary (2^\circ), and tertiary (3^\circ) alcohols are classified based on the number of carbon atoms attached to the carbon bonded to the -OH group (carbinol carbon).

  • Primary: The carbinol carbon is bonded to one other carbon atom.

  • Secondary: The carbinol carbon is bonded to two other carbon atoms.

  • Tertiary: The carbinol carbon is bonded to three other carbon atoms.

  • Methanol is unique and does not fit into the primary, secondary, or tertiary classification.

ALCOHOL CLASSIFICATIONS

• Methanol: No carbons attached to the carbinol carbon.

• Primary alcohol: One carbon attached to the carbinol carbon.

• Secondary alcohol: Two carbons attached to the carbinol carbon.

• Tertiary alcohol: Three carbons attached to the carbinol carbon.

• A quaternary alcohol does not exist.

ALCOHOLS - EXAMPLES AND CLASSIFICATIONS

• n-butyl alcohol (1-butanol): Primary alcohol, boiling point 118 °C, chemical formula: CH2-CH2-CH2-CH2-OH

• isobutyl alcohol (2-methyl-1-propanol): Primary alcohol, boiling point 108 °C, chemical formula: CH2-CH(CH3)-CH_2-OH

• sec-butyl alcohol (2-butanol): Secondary alcohol, boiling point 99 °C, chemical formula: CH3-CH(OH)-CH2-CH_3

• t-butyl alcohol (2-methyl-2-propanol): Tertiary alcohol, boiling point 82 °C, chemical formula: CH3-C(CH3)_2-OH

EXPERIMENTAL RESULTS

1. Chromic Acid Test

   • Distinguishes primary (1^\circ) and secondary (2^\circ) alcohols from tertiary (3^\circ) alcohols.

   • Positive result: Color change from orange to green.

   • n-butyl alcohol: Positive

   • sec-butyl alcohol: Positive

   • tert-butyl alcohol: Negative

Chromic Acid Test Equations

• Primary alcohol reaction: RCH2OH + H2CrO_4 \rightarrow RCHO + Cr^{+3}

  • Primary alcohols are oxidized to aldehydes

• Secondary alcohol reaction: R2CHOH + H2CrO4 \rightarrow R2CO + Cr^{+3}

  • Secondary alcohols are oxidized to ketones

• Tertiary alcohols do not react with chromic acid.

Experimental Results

1. Lucas Test

   • Distinguishes tertiary (3^\circ) and secondary (2^\circ) alcohols from primary (1^\circ) alcohols.

   • Lucas reagent: Mixture of HCl and ZnCl_2

   • Positive result: Formation of an insoluble layer or cloudiness.

   • Reactivity:

     • 3° ROH: Positive (Cloudiness)

     • 2° ROH: Positive (Cloudiness)

     • 1° ROH: Negative (No Cloudiness)

     • Benzylic alcohols: Positive (Cloudiness)

Lucas Test Observations

• tert-butyl alcohol: Cloudiness seen immediately

• benzyl alcohol: Cloudiness seen immediately

• sec-butyl alcohol: Cloudiness seen after 5-6 minutes

• n-butyl alcohol: No cloudiness

Lucas Test Equation

• Example with tert-butyl alcohol: (CH3)3COH + HCl \xrightarrow{ZnCl2} (CH3)3CCl + H2O

Structures of Benzyl Alcohol

• Structure: C6H5CH_2OH

Reactivity

• The reactivity of benzyl alcohol in the Lucas test is due to the stabilization of the benzyl carbocation.

Esterification Reaction

• Alcohol + Carboxylic Acid \rightleftharpoons Ester + Water

• General Equation: ROH + R'COOH \rightleftharpoons R'COOR + H_2O

• Esters have a pleasant odor.

Example

• Salicylic acid + Methanol \rightleftharpoons Methyl Salicylate (Oil of Wintergreen) + Water

• Reaction:

  • C6H4(OH)COOH + CH3OH \xrightarrow{H^+} C6H4(OH)COOCH3 + H_2O

Methyl Salicylate

• Counterirritant found in:

  • Efficascent Oil, Katinko Ointment, Omega Pain Killer

TEST FOR METHYL ALCOHOL

• Methanol + Copper (\Delta) -> Methanal (Formaldehyde) + Pink Color

• H-CHO-H + Cu \xrightarrow{\Delta} H-C=O + H

Iodoform Test

• Positive for compounds containing the acetyl group (CH_3CO) like methyl ketones, and secondary alcohols that undergo oxidation to form the acetyl group.

• Ethyl alcohol is the only primary alcohol that gives a positive result.

• Positive Result: Formation of a yellow precipitate of CHI_3 or iodoform

  • ethyl alcohol: Positive (yellow precipitate)

  • isopropyl alcohol: Positive (yellow precipitate)

  • methyl alcohol: Negative

Iodoform Test Reactions

• ethanol + aqueous iodine + NaOH → iodoform

• Oxidation: CH3CH2OH \rightarrow CH_3CHO

• Substitution: CH3CHO \rightarrow CCl3CHO

• Hydrolysis: CCl3CHO + NaOH \rightarrow CHCl3 + HCOONa

Iodoform Test - Oxidation of Secondary Alcohols

• Secondary alcohols with an adjacent methyl group are oxidized to methyl ketones by iodine bleach.

• R-CH(OH)-CH3 + I2 + 2NaOH \rightarrow R-CO-CH3 + 2NaI + 2H2O

Iodoform Test - byproduct formation

• CH3-CO-R \xrightarrow{I2, NaOH} CHI_3(s) + RCOONa

Acrolein Test

• Test for glycerol.

• Glycerol \xrightarrow{KHSO_4, \Delta} Acrolein + Water

• Acrolein (propenal) has a pungent odor.

• CH2OH-CHOH-CH2OH + KHSO4 \rightarrow CH2=CH-CHO + 2H_2O

Fermentation

• Glucose \xrightarrow{yeast, zymase} 2 C2H5OH + 2 CO_2

• C6H{12}O6 \xrightarrow{yeast, zymase} 2 C2H5OH + 2 CO_2

Other examples:

• Glucose \xrightarrow{Aspergillus} Pyruvate

• Pyruvate \xrightarrow{Lactobacillus} Lactic acid

• Glucose \xrightarrow{Saccharomyces} Ethanol + CO_2

Fermentation Examples

• Soy sauce, cheese, yogurt (lactic acid fermentation)

• Beer, wine (ethanol fermentation)

• Bread (ethanol and carbon dioxide production)

USES OF ALCOHOLS

• Perfume

• Drinks

• Starter

• Solvent

• Antiseptic

• Fuel

Uses of Alcohols

• Disinfectants

• Solvents

• Liquor

• High-efficiency fuels

• Used to synthesize other organic compounds

• Fungicides

• Cosmetics

• Used to make vinegar

• Used in the manufacturing of plastics

PHENOLS

Experiment 14

PHENOL (Ar-OH)

• Aromatic organic compound with the formula C6H5OH.

• White crystalline solid that is volatile.

• Mildly acidic.

• Corrosive and toxic.

LIQUID PHENOL

• Liquid Phenol has over 50% phenol

• Colorless when pure, otherwise pink or red.

• Commonly utilized in the medical industry for formulation of various chemicals.

OTHER PHENOLIC COMPOUNDS

• Phenols do not behave as organic alcohols.

• Examples:

  • Catechol

  • Thymol

  • Naphthol

EXPERIMENTAL RESULTS

1. Solubility in Alkali

   • Phenol reacts with NaOH solution to give a colorless solution containing sodium phenoxide.

2. Reaction with FeCl_3

   • Phenol gives a violet color when treated with dilute FeCl_3.

   • Phenol + FeCl3 \rightarrow [Fe(Phenol)6]^{3+} + 3HCl

Reaction with FeCl_3

• Other phenolic compounds give colored complexes when reacted with FeCl_3.

• The color is due to ferric phenoxide salts.

1. Bromine Water Test

   • Phenol + Bromine Water → 2,4,6-tribromophenol (white precipitate)

   • C6H5OH + 3Br2 \rightarrow C6H2Br3OH + 3HBr

   • Salicylic acid + Bromine → Brominated product

2. Phenolphthalein Formation

   • Phenol + Phthalic anhydride \rightarrow Phenolphthalein.

   • Phenolphthalein is pink with NaOH and clear with HCl.

3. Millon’s Test

   • Test for the presence of a phenolic group in tyrosine and proteins containing tyrosine.

   • Millon’s reagent: HgNO3 in HNO3.

Millon's Test Observation

• Protein + Millon’s reagent → Mercury salt of protein → Flesh to red precipitate.

• Albumin: Gave flesh to red precipitate.

• Phenol: Gave negative result.

ALDEHYDES & KETONES

Experiment 15

ALDEHYDES (RCOH) & KETONES (RCOR)

• Contain a carbonyl group, C=O

• Aldehydes have at least one H attached to the carbonyl group, ketones have two carbon groups attached to the carbonyl group.

• Carbon of the carbonyl group is sp^2 hybridized, trigonal in shape, and bond angle of 120^\circ

• The C=O bond is polar.

Formula & Structure

• Carbonyl Group: C=O

• Aldehyde Structure: RCHO

• Ketone Structure: RCOR'

Uses of Aldehydes & Ketones

• High molar mass aldehydes & ketones have fragrant or penetrating odors

• Aromatic aldehydes often used as flavoring agents

  • Almond odor (benzaldehyde) & Cinnamon odor (cinnamonaldehyde)

Common Uses

• Formaldehyde (methanal): Preservative

• Acetone (propanone): Solvent for plastics, nail polish removers, etc.

Physical Properties

• Aldehydes and Ketones have higher boiling points than hydrocarbons, but lower boiling points than alcohols, because they have no H attached to the O.

• Aldehydes and Ketones have strong odors and are often used as flavorings or scents.

• Small aldehydes are reasonably soluble in water.

• Large aldehydes are less polar and dissolve more readily in nonpolar organic solvents.
  A. Test for Carbonyl group (C=O)

1. 2,4-DNPH (Brady's) Test

   • Used to differentiate aldehydes and ketones from other types of carbonyl-containing organic compounds.

   • A solution of 2,4-dinitrophenylhydrazine (2,4-DNPH) in ethanol tests for aldehydes or ketones.

   • Most aldehydes or ketones react with the orange reagent to give a red, orange, or yellow precipitate.

   • Examples

     • acetophenone

     • benzaldehyde

     • formaldehyde

     • acetone

   • Observation

     • All test compounds gave a positive result of yellow to red 2,4-dinitrophenylhydrazone.

2,4-DNPH Reaction

• aldehyde RCHO :(aq) + 2,4-DNPH -> hydrazone ppt

• ketone RCOR' :(aq) + 2,4-DNPH -> hydrazone ppt

1. Sodium Bisulfite Test

   • Positive result: White precipitate

   • Acetone and acetaldehyde gave white precipitate.

2. Sodium Bisulfite test equation

   • R-CHO + NaHSO3 \rightarrow R-CH(OH)-SO3Na

   • R-CO-CH3 + NaHSO3 \rightarrow R-C(OH)(SO3Na)-CH3

B. Test for Aldehydes

1. Schiff’s Test

   • Test for aliphatic and aromatic aldehydes.

   • Schiff’s Reagent is a reaction product of fuchsine or closely related pararosaniline and NaHSO_3.

Schiff's Test Observation

• Positive result: Violet-colored complex

• Formalin & benzaldehyde gave (+) result

• Acetone & acetophenone gave (-) result

Schiff's Reaction

• aldehyde + Schiff's reagent \rightarrow violet colored product

• R-CHO + HSO_3Na + fuchsine -> product of violet color

1. Tollen’s Test

   • Test for aliphatic aldehyde

   • Positive result: Silvery or mirror-like substance

   • Tollens' reagent is an alkaline solution of ammoniacal AgNO3.

   • [Ag(NH3)_2]^+

Tollen's Test Result

• Formalin and glucose gave (+) result

• Benzaldehyde and acetone gave (-) result

Tollen’s Test Reaction

• aldehyde: RCHO + 2[Ag(NH3)2]OH -> 2Ag + RCOONH4 + 3NH3 + H_2O

1. Fehling’s Test

   • Test for aliphatic aldehydes

   • Fehling’ s Reagent is made up of two separate solutions known as Fehling's A and Fehling's B.

Fehling's Test Observation

• Positive Result: Yellow to brick-red precipitate

• Formalin and glucose gave (+) result

• Benzaldehyde and acetone gave (-) result

Fehling's Test Equation

• RCHO + 2Cu^{2+} + 4OH^- \rightarrow RCOO^- + Cu2O + H2O

C. Test for Methyl Ketones

1. Sodium Nitroprusside Test

   • Used in clinical tests to detect the presence of ketone in urine

   • Positive result: Bright red to wine red color

Positive Results

• Acetone gave (+) result

• ethyl methyl ketone gave (+) result

1. Iodoform Test

   • Used to detect presence of methyl ketones

   • Positive result: Yellow precipitate of CHI_3 or iodoform

Iodoform Test Results

• Acetone gave (+) result

• Ethyl methyl ketone gave (+) result

• Ethyl acetate gave (-) result

Iodoform Test Reaction

• methyl ketoneRCOCH3 + 3I2 + 4NaOH -> RCOONa + CHI3 + 3NaI + 3H2O

D. Test for Benzaldehyde

• Benzaldehyde Oxidation → Benzoic acid

• (0) \xrightarrow{Benzaldehyde} C6H5COOH \text {white substance}

E. Molisch Test

• General test for carbohydrates

• Molisch's reagent (α-naphthol dissolved in ethanol)

• Positive result: Violet layer or ring

Molisch Test Results

• Glucose and starch gave (+) result

• Benzaldehyde gave (-) result

Molish test equation

• Monosaccharide + \alpha-naphthol \xrightarrow{H2SO4} purple complex

F. Bial’s Orcinol Test

• Used to differentiate hexoses from pentoses

• Bial’s orcinol reagent is composed of orcinol, HCl and ferric chloride

Observations

• Glucose gave a brown colored solution

• Ribose gave a blue to green colored solution

CARBOXYLIC ACIDS & DERIVATIVES

Experiment 16

Carboxylic Acid Structure

• Carboxylic acids are compounds containing a carboxy group (COOH).

• The structure of carboxylic acids is often abbreviated as RCOOH or RCO2H.

Carboxy Group Structure

• R-COOH

• The central carbon atom of the functional group is doubly bonded to one oxygen atom and singly bonded to another.

Physical Properties of Carboxylic Acid

• The carboxyl group of the carboxylic acid consists of a carbonyl group and a hydroxyl group

• Both are very polar

• This means carboxylic acids are polar

• They bond to each other through H-bonding as well as to water molecules

• Because of the strong intermolecular bonds of the H-bonds, they boil at higher temps than aldehydes, ketones or alcohols of similar molecular mass

Carboxylic acid & derivatives

List

• carboxylic acid

• acyl (or acid) chloride

• acid anhydride

• ester

• amide

Carboxylic Acid & Derivatives Table

2. Test for Carboxylic Acid

   1. 1 Reaction with Water and Indicators

      • Carboxylic Acid + Water \rightleftharpoons Carboxylate + Hydronium Ion

      • Acetic Acid + Water \rightleftharpoons Acetate + Hydronium Ion

      • (CH3COOH) + H2O = (CH3COO^-) + H3O^+

   2. 2 Reaction with NaOH

      • (CH3COOH) + NaOH => (CH3COO^-Na^+) + H_2O

   3. 3 Observations

      • Test Compounds:

        • Acetic acid:

          • Miscible with water

          • Blue litmus paper changed to red

          • Methyl orange became reddish in color

          • Miscible with sodium hydroxide

        • Stearic acid

          • Insoluble in water

          • No change in blue litmus paper

          • Methyl orange became yellowish

          • Insoluble in sodium hydroxide

   4. 4 Reaction with Na2CO3

      • Used to differentiate carboxylic acids (RCOOH) from weaker acids like alcohols and phenols.

Test reagent table

5.  5 Esterification

    *   Alcohol + Carboxylic Acid  \rightleftharpoons  Ester + Water
    *   Acetic Acid + n-propyl alcohol  \rightleftharpoons  Propyl acetate (Pleasant Odor) + Water
    *   RCOOH + ROH \rightleftharpoons RCOOR + H_2O

6.  6 Reaction with Neutral FeCl_3

    *   Ferric salts are used as the basis for specific tests for acetic acid and tartaric acid.
    *   The salts of these acids form insoluble colored salts with neutral ferric chloride.

7.  7 Observations

    *   Acetic acid, when reacted with neutral ferric chloride, forms a red-orange solution with a reddish-brown precipitate.
    *   Alpha hydroxyl polycarboxylic acids such as tartaric acid and citric acid form soluble complex salts with ferric chloride.
    *   Tartaric acid, when reacted with neutral ferric chloride, forms a soluble yellow-colored solution.

8.  8 Test Results

    *   Acetic acid: Produced a red-orange solution with a reddish-brown precipitate
    *   Tartaric acid: Produced a soluble yellow-colored solution

3. Special test for citric acid & tartaric acid

   • Citric and tartaric acids are differentiated by the reduction products formed with alkaline potassium permanganate.

   • A green colored solution of K2MnO4 is produced from citric acid.

   • Hydrated manganese dioxide, a brown precipitate, is obtained with tartaric acid.

   1. 1 Special Test Equations

      • Test Compounds

        • Citric Acid: Produced a green colored solution

        • Tartaric acid: Produced a brown precipitate

4. Hydroxamic Test for Esters

   • Hydroxamic test is a test for carboxylic acid derivatives such as esters, acid chlorides, and anhydrides.

   • During the preliminary test, a yellow colored solution is formed.

   • In the final test, magenta or burgundy color is produced when added with ferric chloride.

   1. 1 Observations

      • Positive result