chapter 8: alkanes + intro to IUPAC nomenclature

What’s the general formula for acyclic alkanes?

CₙH₂ₙ₊₂

Example: Propane = C₃H₈.

2(3) + 2 - 8 = 0.

What prefix corresponds to 1–12 carbons?

1 meth-, 2 eth-, 3 prop-, 4 but-, 5 pent-, 6 hex-, 7 hept-, 8 oct-, 9 non-, 10 dec-, 11 undec-, 12 dodec-.

Example: 8 carbons → octane.

How do you name cyclic alkanes?

Add cyclo- + parent name.

Example: Cyclohexane.

Step 1 of IUPAC naming:

Find the longest continuous carbon chain → parent name.

Example: Longest chain = 8 → octane.

Step 2 of IUPAC naming:

Identify substituents (anything off the parent chain besides H).

Example: CH₃ substituent = methyl.

What suffix is used for alkane substituents?

What suffix is used for alkane substituents?

A: -yl

Example: CH₃– = methyl, C₂H₅– = ethyl.

Step 3: how do you number the parent chain?

Number to give substituents the lowest possible number.

Example: 3-methyloctane (not 6-methyloctane).

Step 4: how do you order substituents in the name?

Alphabetize substituents in the written name.

Example: 2-bromo-6-methyloctane (b before m).

How do you name molecules with multiple identical substituents?

Use prefixes: di-, tri-, tetra-, penta-; don’t use these for alphabetizing.

Example: 2,2-dibromohexane.

What does “2,5,5-tribromo-6-chloro-3-ethyloctane” teach you?

List substituents alphabetically (bromo, chloro, ethyl) while keeping their locants; prefixes like “tri-” don’t affect alphabetizing.

Example: You still alphabetize by “bromo,” not “tri.”

Propyl vs isopropyl—what’s the difference?

Propyl attaches from an end carbon; isopropyl attaches from the middle carbon.

Example: 5-propylnonane vs 5-isopropylnonane.

Butyl substituent types you must recognize:

n-butyl, sec-butyl, isobutyl, tert-butyl.

Example: 6-tert-butylundecane has attachment at a tertiary carbon.