Chapter 10 Fatty Acid Nomenclature

What prefix corresponds to a 2-carbon fatty acid?

eth- → ethanoic acid (acetic acid) → CH₃COOH

What prefix corresponds to a 3-carbon fatty acid?

prop- →propanoic acid (propionic acid) → CH₃CH₂COOH

What prefix corresponds to a 4-carbon fatty acid?

but- →butanoic acid (butyric acid) → CH₃(CH₂)₂COOH

What prefix corresponds to a 5-carbon fatty acid?

pent- → pentanoic acid (valeric acid) → CH₃(CH₂)₃COOH

What prefix corresponds to a 6-carbon fatty acid?

hex- → hexanoic acid (caproic acid) → CH₃(CH₂)₄COOH

What prefix corresponds to an 8-carbon fatty acid?

oct- → octanoic acid (caprylic acid) → CH₃(CH₂)₆COOH

What prefix corresponds to a 10-carbon fatty acid?

dec- → decanoic acid (capric acid) → CH₃(CH₂)₈COOH

What prefix corresponds to a 12-carbon fatty acid?

dodec- → dodecanoic acid (lauric acid) → CH₃(CH₂)₁₀COOH

What prefix corresponds to a 14-carbon fatty acid?

tetradec- → tetradecanoic acid (myristic acid) → CH₃(CH₂)₁₂COOH

What prefix corresponds to a 16-carbon fatty acid?

hexadec- → hexadecanoic acid (palmitic acid) → CH₃(CH₂)₁₄COOH

What prefix corresponds to an 18-carbon fatty acid?

ctadec- → octadecanoic acid (stearic acid) → CH₃(CH₂)₁₆COOH

What prefix corresponds to a 20-carbon fatty acid?

eicos- → eicosanoic acid (arachidic acid) → CH₃(CH₂)₁₈COOH

What prefix corresponds to a 22-carbon fatty acid?

docos- → docosanoic acid (behenic acid) → CH₃(CH₂)₂₀COOH

What prefix corresponds to a 24-carbon fatty acid?

tetracos- → tetracosanoic acid (lignoceric acid) → CH₃(CH₂)₂₂COOH

What suffix indicates a saturated fatty acid?

-anoic acid → No double bonds

What suffix indicates one double bond?

-enoic acid → 1 double bond

What suffix indicates two double bonds?

-dienoic acid → 2 double bonds

What suffix indicates three double bonds?

-trienoic acid → 3 double bonds

What suffix indicates four double bonds?

-tetraenoic acid → 4 double bonds

What’s the difference between “-anoic” and “-enoic” acids?

• anoic acid → no double bonds (saturated)

• -enoic acid → one or more double bonds (unsaturated)

Which type (saturated or unsaturated) is solid at room temperature?

Saturated fatty acids (e.g., palmitic, stearic)

Which type is liquid at room temperature?

Unsaturated fatty acids (e.g., oleic, linoleic, linolenic)

Which type of fatty acids are found in animal fats?

Saturated fatty acids

Which type of fatty acids are found in plant and fish oils?

Unsaturated fatty acids + because they remain liquid at room temperature and include various types such as omega-3 and omega-6 fatty acids.

What is the common name for hexadecanoic acid (16:0)?

Palmitic acid (saturated, found in palm oil)

What is the common name for octadecanoic acid (18:0)?

Stearic acid (saturated, found in animal fats)

What is the common name for cis-9-octadecenoic acid (18:1 Δ⁹)?

Oleic acid (monounsaturated, olive oil)

What is the common name for cis,cis-9,12-octadecadienoic acid (18:2 Δ⁹,¹²)?

Linoleic acid (polyunsaturated, ω–6, sunflower oil)

What is the common name for cis,cis,cis-9,12,15-octadecatrienoic acid (18:3 Δ⁹,¹²,¹⁵)?

α-Linolenic acid (ALA) (polyunsaturated, ω–3, flaxseed oil)

What is the common name for cis-5,8,11,14-eicosatetraenoic acid (20:4 Δ⁵,⁸,¹¹,¹⁴)?

Arachidonic acid (polyunsaturated, ω–6, signaling lipid precursor)

What is the common name for cis-5,8,11,14,17-eicosapentaenoic acid (20:5 ω–3)?

EPA (omega-3, found in fish oils)

What is the common name for cis-4,7,10,13,16,19-docosahexaenoic acid (22:6 ω–3)?

DHA (omega-3, important for brain and retina)

How does chain length affect melting point?

Longer chain = higher melting point

How does the number of double bonds affect melting point?

More double bonds = lower melting point

Why do cis double bonds make fatty acids liquid?

They introduce “kinks” that prevent tight packing, lowering melting point.

What do trans double bonds do to fatty acid structure?

They make the chain straight (like saturated fats), allowing tighter packing.

What are trans fats made by?

Partial hydrogenation of unsaturated oils to increase shelf life and stability.

Why are trans fats harmful?

They raise LDL (“bad”) cholesterol and increase cardiovascular disease risk.

Which fatty acids are essential for humans?

Linoleic acid (ω–6) and α-Linolenic acid (ω–3) — must be obtained from diet as they cannot be synthesized by the body.

What is the relationship between ALA, EPA, and DHA?

ALA (from plants) → converted to EPA → converted to DHA (in body, limited conversion)