Chapter 13: Organic Chemistry

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Chapter Overview & SLOs

What is organic chemistry? Organic chemistry is the branch of chemistry that studies carbon-containing compounds (with some exceptions like carbonates, carbides, and oxides of carbon). Organic compounds form the basis of life and are found in fuels, plastics, medicines, and food.

Why is carbon unique? Carbon can form four covalent bonds (tetravalent) and can bond with other carbon atoms to form long chains and rings (catenation), leading to millions of organic compounds.

What are hydrocarbons? Hydrocarbons are organic compounds composed only of carbon and hydrogen atoms.

How do we classify hydrocarbons? Hydrocarbons are classified into two main categories:

• Saturated hydrocarbons (Alkanes): Contain only single carbon-carbon bonds ($C-C$). They are called alkanes with general formula $C_nH_{2n+2}$.
• Unsaturated hydrocarbons: Contain double or triple carbon-carbon bonds.
  • Alkenes: Contain at least one double bond ($C=C$). General formula: $C_nH_{2n}$.
  • Alkynes: Contain at least one triple bond ($C\equiv C$). General formula: $C_nH_{2n-2}$.

What are alkane stems (prefixes)? The prefix indicates the number of carbon atoms in the longest continuous chain:

| Prefix | Number of Carbon Atoms | Example | |--------|----------------------|---------| | Meth- | 1 | Methane $CH_4$ | | Eth- | 2 | Ethane $C_2H_6$ | | Prop- | 3 | Propane $C_3H_8$ | | But- | 4 | Butane $C_4H_{10}$ | | Pent- | 5 | Pentane $C_5H_{12}$ | | Hex- | 6 | Hexane $C_6H_{14}$ | | Hept- | 7 | Heptane $C_7H_{16}$ | | Oct- | 8 | Octane $C_8H_{18}$ | | Non- | 9 | Nonane $C_9H_{20}$ | | Dec- | 10 | Decane $C_{10}H_{22}$ |

What are functional groups? A functional group is an atom or group of atoms that gives a family of organic compounds its characteristic chemical and physical properties.

| Functional Group | Name | Family | General Formula | Example | |-----------------|------|--------|----------------|---------| | $-OH$ | Hydroxyl | Alcohols | $R-OH$ | $CH_3OH$ (Methanol) | | $-COOH$ | Carboxyl | Carboxylic acids | $R-COOH$ | $CH_3COOH$ (Acetic acid) | | $C=O$ | Carbonyl | Aldehydes (end) / Ketones (middle) | $R-CHO$ (Aldehyde), $R-CO-R'$ (Ketone) | $CH_3CHO$ (Acetaldehyde) | | $-NH_2$ | Amino | Amines | $R-NH_2$ | $CH_3NH_2$ (Methylamine) | | $-COO-$ | Ester | Esters | $R-COO-R'$ | $CH_3COOCH_3$ (Methyl acetate) | | $-O-$ | Ether | Ethers | $R-O-R'$ | $CH_3-O-CH_3$ (Dimethyl ether) |

What are structural formulas and condensed formulas?

• Structural formula: Shows the arrangement of atoms and bonds in a molecule.
• Condensed formula: A simplified notation showing how atoms are grouped together.

| Compound | Molecular Formula | Condensed Formula | Structural Formula | |----------|------------------|-------------------|-------------------| | Methane | $CH_4$ | $CH_4$ | H-C-H (with 4 H atoms) | | Ethane | $C_2H_6$ | $CH_3-CH_3$ | H-C-C-H (with 3 H per C) | | Ethanol | $C_2H_6O$ | $CH_3-CH_2-OH$ | H-C-C-O-H | | Ethene | $C_2H_4$ | $CH_2=CH_2$ | H-C=C-H (double bond) | | Ethyne | $C_2H_2$ | $CH\equiv CH$ | H-C$\equiv$C-H (triple bond) |

What is the carbon bonding rule? Every carbon atom must have exactly four covalent bonds (tetravalency). This is the most important rule when drawing organic structures.

What is a homologous series? A homologous series is a family of organic compounds with the same functional group and general formula, where each successive member differs by a $CH_2$ group.

• Alkanes series: $CH_4$ (methane), $C_2H_6$ (ethane), $C_3H_8$ (propane), $C_4H_{10}$ (butane)...
• Alkenes series: $C_2H_4$ (ethene), $C_3H_6$ (propene), $C_4H_8$ (butene)...
• Alcohols series: $CH_3OH$ (methanol), $C_2H_5OH$ (ethanol), $C_3H_7OH$ (propanol)...

What are some practical applications of organic compounds?

• Aspirin (acetylsalicylic acid): Contains carboxyl group ($-COOH$) and carbonyl group ($C=O$). Used as a pain reliever and anti-inflammatory.
• PVC (Polyvinyl chloride): An unsaturated polymer (contains double bonds). Used for pipes, cables, and construction materials.
• Ethanol ($C_2H_5OH$): Used in plastics, cosmetics, beverages, and as a disinfectant.
• Methane ($CH_4$): Main component of natural gas, used as fuel.
• Ethene ($C_2H_4$): Used to ripen fruits and to make polyethylene (plastic).

Examples of saturated vs unsaturated compounds:

• Saturated: Butane ($C_4H_{10}$) — only single bonds.
• Unsaturated: Propene ($CH_3-CH=CH_2$) — contains double bond; Vinyl chloride ($CH_2=CHCl$) — contains double bond.

These notes are strictly aligned with the Student Learning Outcomes (SLOs) for the FBISE 2026 annual examination.

• How do we differentiate between saturated and unsaturated compounds? Classify molecules like Propene and Vinyl Chloride as unsaturated due to their double bonds ($C=C$), while identifying Butane ($C_4H_{10}$) as a saturated hydrocarbon (contains only single bonds $C-C$).
• How do we identify functional groups in complex molecules? Recognize and encircle specific groups like hydroxyl ($-OH$), carboxyl ($-COOH$), carbonyl ($C=O$), amines ($-NH_2$), esters ($-COO-$), and ethers ($-O-$) within structural diagrams to classify the parent compound (e.g., alcohol, carboxylic acid, aldehyde/ketone, amine, ester, ether).
• How do we draw structural and condensed formulas? Sketch the full carbon-hydrogen arrangements for simple alkanes like methane ($CH_4$), ethane ($CH_3-CH_3$), and propane ($CH_3-CH_2-CH_3$), and convert them into condensed forms for compounds like ethanol ($CH_3-CH_2-OH$) and acetic acid ($CH_3-COOH$).
• How do we apply the principles of homologous series? Use general formulas to predict the molecular structure of compounds with specific carbon counts, such as an alkane with 5 carbons ($C_5H_{12}$), an alkene with 4 carbons ($C_4H_8$), or an alkyne with 4 carbon atoms ($C_4H_6$).

Frequently Asked Questions (FAQ)