naming IUPAC

Step 1: Find the parent chain (the “main road”)

    •    Look for the longest continuous chain of carbon atoms.

    •    Count the carbons (corners + ends in a line-angle diagram).

    •    This gives the prefix:

    •    1 meth, 2 eth, 3 prop, 4 but, 5 pent, 6 hex, 7 hept, 8 oct, 9 non, 10 dec

Step 2: Decide the ending (what kind of bonds?)

    •    If the chain has only single bonds → ending -ane (alkane)

    •    If it has a double bond → ending -ene (alkene)

    •    If it has a triple bond → ending -yne (alkyne)

(For your unit right now, you’ll mostly see -ane and some -ene.)

Step 3: Number the parent chain

You number the carbons 1, 2, 3, … from the end that gives the lowest possible number to the most important thing.

Use this priority:

    1.    Double/triple bond location (if there is one) gets the lowest number

    2.    Then branches/substituents get the lowest numbers

Simple rule:

    •    Start numbering from the end that hits the first “important thing” sooner.

Step 4: Identify substituents (the “decorations”)

Anything attached to the parent chain but not part of it is a substituent.

Common ones:

    •    F = fluoro

    •    Cl = chloro

    •    Br = bromo

    •    I = iodo

    •    CH₃ = methyl

    •    CH₂CH₃ = ethyl

Step 5: Give each substituent an address (a number)

    •    Write the carbon number where each substituent is attached.

    •    If there are two or more of the same substituent:

    •    di = 2, tri = 3, tetra = 4

    •    Example: 2,3-dichloro (two chlorines on carbons 2 and 3)

Step 6: Put substituents in alphabetical order

    •    Ignore di/tri/tetra when alphabetizing.

    •    Example: chloro comes before methyl.

Step 7: Write the full name

(numbers)-(substituents) + parent name

Example format:

    •    3-chloro-1-methylpentane

    •    parent chain: pentane

    •    substituents: chloro at 3, methyl at 1

    •    alphabetical order: chloro then methyl