chemistry

1. Hydrocarbons

Hydrocarbons are compounds containing only carbon (C) and hydrogen

(H).

A) Saturated Hydrocarbons

 Contain only single bonds (C–C).

 Also called Alkanes.

 General formula: CnH2n+2

Example: Methane (CH4), Ethane (C2H6), Propane (C3H8)

B) Unsaturated Hydrocarbons

 Contain double or triple bonds.

 Include Alkenes (C=C) and Alkynes (C≡C).

 General formulas:

o Alkene: CnH2n

o Alkyne: CnH2n−2

Example:

 Alkene: Ethene (C2H4) → double bond

 Alkyne: Ethyne (C2H2) → triple bond

Name:

Class:

Date:

IUPAC Naming of Hydrocarbons

Step-by-Step Rules

1. Find the longest continuous chain of carbon atoms → base name.

o Alkane → “-ane”, Alkene → “-ene”, Alkyne → “-yne”

2. Number the chain from the end nearest a multiple bond or

substituent.

3. Identify and name substituents (side groups).

o Alkyl groups: methyl (–CH3), ethyl (–C2H5), propyl (–C3H7)

4. Combine substituents with numbers indicating their position.

o Example: 2-methylpropane, 3-ethylpentane

5. For multiple bonds: indicate position of double/triple bond.

o Example: But-2-ene (double bond starts at C-2)

Examples of Hydrocarbon Naming

Compound Type IUPAC Name Notes

CH4 Alkane Methane Saturated, single C

CH3–CH3 Alkane Ethane Saturated

CH2=CH2 Alkene Ethene Double bond starts at

C-1

CH≡CH Alkyne Ethyne Triple bond starts at C-

CH3–CH=CH–CH3 Alkene But-2-ene Double bond at C-2

CH3–CH(CH3)–

CH3

Alkane 2-

Methylpropane

Methyl substituent on

C-2

2. Cycloalkanes

Definition

 Cycloalkanes are saturated hydrocarbons in which carbon atoms

are arranged in a ring.

 General formula: CnH2n (same as alkenes, but all single bonds).

 Saturated → only single C–C bonds.

Structure

 Carbon atoms are connected in a closed loop (ring).

 Hydrogen atoms are attached to satisfy 4 bonds per carbon.

 Rings can be small (3–5 carbons) or larger (6+ carbons).

Examples:

 Cyclopropane → 3 carbon ring → C3H6

 Cyclobutane → 4 carbon ring → C4H8

 Cyclopentane → 5 carbon ring → C5H10

 Cyclohexane → 6 carbon ring → C6H12

IUPAC Naming Rules for Cycloalkanes

1. Base name: Use “cyclo-” + alkane name corresponding to

number of carbons in the ring.

o Cyclopropane (3 carbons), Cyclobutane (4 carbons), etc.

2. Number the ring: Start from the carbon with the substituent.

3. Substituents:

o Alkyl groups or other functional groups are named and

numbered to give lowest locants.

o If only one substituent → no need to number.

4. Multiple substituents:

o Number to give lowest set of numbers.

o List substituents alphabetically.

Examples of Cycloalkane Naming

Structure Name Notes

3-carbon ring with

no substituents

Cyclopropane Smallest ring

4-carbon ring with

one methyl group

1-Methylcyclobutane Number starts at

substituent

6-carbon ring with

two methyl groups

1,3-

Dimethylcyclohexane

Number to give lowest

locants, alphabetical

order

5-carbon ring with

ethyl & methyl

1-Ethyl-3-

methylcyclopentane

Alphabetical order for

naming substituents

Key Points

 Cycloalkanes are saturated → only single bonds.

 General formula: CnH2n → fewer H than straight-chain alkanes

because ring closes.

 Naming uses “cyclo-” prefix.

 Ring can have substituents, which must be numbered to give

lowest locants.

 Small rings (3–4 carbons) are strained, larger rings (5–6) are

more stable.

3. Alcohols (–OH Group)

 Organic compounds containing the hydroxyl group (–OH)

attached to a carbon atom.

 General formula: R–OH

Types of Alcohols

1. Primary (1°): –OH attached to a carbon bonded to one other

carbon (or none).

o Example: CH3–CH2–OH (Ethanol)

2. Secondary (2°): –OH attached to a carbon bonded to two other

carbons.

o Example: CH3–CHOH–CH3 (Propan-2-ol)

3. Tertiary (3°): –OH attached to a carbon bonded to three other

carbons.

o Example: (CH3)3C–OH (2-Methylpropan-2-ol)

IUPAC Naming Rules

1. Find longest chain containing –OH → base name.

2. Replace “-e” of alkane with “-ol”.

3. Number chain from end nearest –OH group.

4. Name substituents as usual.

Examples:

 CH3–CH2–OH → Ethanol (1°)

 CH3–CHOH–CH3 → Propan-2-ol (2°)

 (CH3)3C–OH → 2-Methylpropan-2-ol (3°)

4. Aldehydes (–CHO Group)

 Contain carbonyl group (C=O) at the end of the chain.

 General formula: R–CHO

IUPAC Naming Rules

1. Longest chain containing –CHO → base name.

2. Replace “-e” of alkane with “-al”.

3. Numbering starts at carbon of –CHO group (always C-1).

4. Name substituents as usual.

Examples:

 Methanal → H–CHO (Formaldehyde)

 Ethanal → CH3–CHO (Acetaldehyde)

 Propanal → CH3–CH2–CHO

Quick Summary Table: Hydrocarbons & Functional Groups

Compound Type General

Formula

Key Feature Example

Alkane

(saturated)

CnH2n+2 Single bonds only Methane,

Ethane

Alkene

(unsaturated)

CnH2n One or more C=C

double bonds

Ethene, But-2-

ene

Alkyne

(unsaturated)

CnH2n−2 One or more C≡C

triple bonds

Ethyne

Alcohol R–OH Hydroxyl group Ethanol,

Propan-2-ol

Aldehyde R–CHO Carbonyl at chain

end

Methanal,

Propanal

Real-World in the UAE

cyclohexane’s wide industrial use (in nylon production, paints,

coatings) Because UAE imports much of its cyclohexane,

buyers (industries, labs) rely on international suppliers to

ensure ISO-certified, REACH-compliant, or ACS-standard

cyclohexane to avoid process disruptions and safety risks.

•Parent chain = the ring → name as cyclo + alkane

(e.g., cyclopentane).

•Number the ring to give substituents the lowest

possible numbers.

•One substituent → no number needed (e.g.,

methylcyclohexane).

•Multiple substituents → number, use di-/tri-, and

list alphabetically (e.g., 1-ethyl-3-

methylcyclobutane).

•If the side chain is longer than the ring → name

the ring as a substituent (e.g., cyclopropylbutane).

Real-World in the UAE

cyclohexane’s wide industrial use (in nylon production, paints,

coatings) Because UAE imports much of its cyclohexane,

buyers (industries, labs) rely on international suppliers to

ensure ISO-certified, REACH-compliant, or ACS-standard

cyclohexane to avoid process disruptions and safety risks.

1. Identify the Longest Carbon Chain Containing

the Double Bond The parent chain must include

the C=C double bond. Count the number of

carbons in this chain to determine the base

name:2C → ethene3C → propene4C →

butene5C → pentene ... and so on.

2. Number the Chain from the End Nearest the

Double Bond Give the double bond the lowest

possible number. Example: CH2=CH–CH3 → the

double bond starts at C1 → prop-1-ene

3. Name and Number Substituents Identify

alkyl or other groups attached to the main

chain. Number the carbon to which the

substituent is attached. Place substituents in

alphabetical order in the name.

Real-World in the UAE

Ethene is the simplest alkene with a C=C double bond.

Uses of ethene: Polymer production: Used to make

polyethylene (plastic bags, bottles).

•Alcohol: Organic compound with a hydroxyl (–OH)

group.

•Hydroxyl group (–OH): Functional group that defines

alcohols.

•Primary (1°) alcohol: –OH attached to a carbon

bonded to one other carbon.

•Secondary (2°) alcohol: –OH attached to a carbon

bonded to two other carbons.

•Tertiary (3°) alcohol: –OH attached to a carbon

bonded to three other carbons.

Definition of Aldehydes

•Aldehydes are organic compounds containing the –CHO

functional group.

•General formula: R–CHO, where R can be a hydrogen or an

alkyl/aryl group.

•The –CHO group consists of a carbonyl carbon (C=O) bonded

to a hydrogen.

•They are often reactive, especially at the carbonyl carbon,

making them important in chemistry and industry.

Step Tip

Find the longest chain containing the –CHO

group.

2 Replace the “-e” of the alkane with “-al”.

Number substituents from the –CHO end

(always C-1).

Remember: –CHO carbon is always C-1, so

straight-chain aldehydes usually don’t need

numbering.

Classification of Alcohols

Based on the carbon bonded to –OH:

1.Primary (1°) – –OH attached to a carbon bonded to 1 other

carbon

1. Example: Ethanol CH3CH2OHCH_3CH_2OHCH3CH2OH

2.Secondary (2°) – –OH attached to a carbon bonded to 2 other

carbons

1. Example: Isopropanol

CH3CHOHCH3CH_3CHOHCH_3CH3CHOHCH3

3.Tertiary (3°) – –OH attached to a carbon bonded to 3 other

carbons

1. Example: Tert-butanol

(CH3)3COH(CH_3)_3COH(CH3)3COH

3. Physical Properties

•Polar molecules → can form hydrogen

bonds

•High boiling points compared to

alkanes of similar size

•Soluble in water (especially smaller

alcohols)

Methanol: solvent, fuel, formaldehyde production