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Chemistry becomes wonderfully organised when you know how to prioritise functional groups. Poly-functional compounds may appear complex, yet once the priority order and naming sequence settle in your mind, the entire structure moves like an orchestra tuned to perfection. This guide presents those rules in a crisp, colourful, and exam-friendly style for students preparing for MDCAT, ECAT, and Board examinations, curated especially for the readers of LearnChemistry by Inam Jazbi.

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🌈🌟 IUPAC Rules for Naming Poly-Functional Compounds | Ultimate MDCAT & ECAT Guide

💠Principle Functional Group

A compound contains two or more different functional groups in a molecule is called Poly-functional or Multifunctional Compound (PFC). The functional group which determines the class of polyfunctional compound is referred to as the Principle Functional Group (PFG) while all the remaining functional groups termed as Subsidiary Functional Group or Substituents (SFG).

e.g.

💠Selection of PFG in PFC

IUPAC has given a chart called Nomenclature Priority Table (NPT) to determine the PFG in PFC to determine its class. A functional group which occurs higher up in the NPT takes precedence over others lying below and is treated as PFG, and it specifies the class of PFC. e.g.

💠Nomenclature Priority Table (NPT)

The above PFC contains two functional group namely olefinic double bond (>C=C<) and hydroxyl group. This compound could be named as an alkene or an alcohol. Since –OH group ranks higher than >C=C< in NPT, therefore, –OH is PFG and compound is named as an alcohol (i.e. –OH group takes preference in numbering).

🎯Examples of Polyfunctional Groups (PFG) Naming with Reason

🌟(I) Alkenol (compound containing both –OH group and olefinic double bond)

The PFC containing both –OH group and olefinic double bond are called Alkenols or Enol. In alkenols, –OH governs the numbering as it ranks higher than >C=C< in NPT. Thus –OH group in enol is a PFG and gets the preference in numbering.

🌟(II) Alkenal (compound containing both –CHO group and olefinic double bond)

The PFC containing both –CHO group and olefinic double bond are called Alkenal. In alkenals, –CHO group governs the numbering as it ranks higher than >C=C< in NPT. Thus –CHO group in alkenal is a PFG and gets the preference in numbering.

🌟(III) Alkenone (Compounds containing both keto group and olefinic double bond)

The PFC containing both keto (–CO) group and olefinic double bond are called Alkenone. In alkenone, keto (–CO–) group governs the numbering as it ranks higher than >C=C< in NPT. Thus –CO– group in alkenone is a PFG and gets the preference in numbering.

🌟(IV) Hydroxyalkanoic acid (Hydroxyalkenoic acid)

Explanation

The PFC containing both –OH group and –COOH group are called Hydroxyalkanoic acid. Double bond containing hydroxyalkanoic acids are called hydroxyalkenoic acid. In these compounds, –COOH group governs the numbering as it ranks higher than –OH (and olefinic double bond) in NPT. Thus –COOH group is a PFG and gets the preference in numbering.

🌟(V) Alkenoic Acid(Compounds containing both carboxylic group and olefinic double bond)

The PFC containing both carboxyl group and olefinic double bond are called Alkenoic acid. In alkenoic acids carboxyl group governs the numbering as it ranks higher than >C=C< in NPT. Thus –COOH group is a PFG and gets the preference in numbering.

🌟(VI) Oxoalkanoic Acid

Explanation

The PFC containing both keto (–CO–) group and –COOH group are called oxoalkanoic acid. In oxoalkanoic acid, –COOH group governs the numbering as it ranks higher than –CO– group in NPT. Thus –COOH group is a PFG and gets the preference in numbering.

🌟(VII) Oxoalkanal / Oxoalkenal

Explanation

The PFC containing both aldo (–CHO) group and keto (–CO–) group are called Oxoalkanal. Double bond containing oxoalkanal are called Oxoalkenal. In these compounds, –CHO group governs the numbering as it ranks higher than keto group (and olefinic double bond) in NPT. Thus –CHO group is a PFG and gets the preference in numbering.

🌟(VIII) Hydroxyalkanoate / Hydroxyalkenoate

Explanation

The PFC containing both ester group and –OH group are called hydroxyalkanoate. Double bond containing hydroxyalkanoate are called hydroxyalkenoate. In these compounds, ester group (–COO–) governs the numbering as it ranks higher than –OH group (and olefinic double bond) in NPT. Thus –COO– group is a PFG and gets the preference in numbering.

🌟(IX) Miscellaneous Examples

Explanation

The above PFC contains three functional groups namely –COOH, –CO– and C=C bond. The –COOH group occupies the top position in NPT and takes precedence over all other functional groups, that is why compound gets the class name alkanoic acid and because there is C=C bond, it is named as alkenoic acid. The ketonic group (–CO–) is treated as substituent and it is indicated by the prefix ‘oxo’ along with a number to indicate its position.

Explanation

The above PFC contains four functional groups namely –CHO, –CO–, –OH and C=C bond. The –CHO group occupies the top position in NPT and takes precedence over all other functional group, that is why compound gets the class name alkanal and because there is C=C bond, it is named as alkenal. The ketonic (–CO–) group and –OH group are treated as substituents and they are indicated by the prefix ‘oxo’ and hydroxy respectively along with a number to indicate their position.

Explanation

The above PFC contains three functional groups namely –COOH, –OH and C=C bond. The – COOH group occupies the top position in NPT and takes precedence over all other functional groups, that is why compound gets the class name alkanoic acid and because there is C=C bond, it is named as alkenoic acid. The hydroxy group (–OH) is treated as substituent and it is indicated by the prefix ‘hydroxy’ along with a number to indicate its position.

🌈 Quick Scan of IUPAC Rules for Naming Poly-Functional Compounds

🔥 1. What Are Poly-Functional Compounds?

Compounds that contain two or more functional groups on the same carbon chain or ring. Naming them requires strict priority rules so the most important group becomes the suffix.

🌟 2. The Core Principle

👉 The functional group with the highest priority gets the suffix and must receive the lowest possible locant.

👉 All other functional groups are named as prefixes.

🎯 3. Priority Order of Functional Groups (Highest to Lowest)

Carboxylic acids (-oic acid)

Sulfonic acids (-sulfonic acid)

Esters (-oate)

Acid chlorides (-oyl chloride)

Amides (-amide)

Nitriles (-nitrile)

Aldehydes (-al)

Ketones (-one)

Alcohols (-ol)

Amines (-amine)

Alkenes/Alkynes (-ene / -yne)

Halogens, Nitro, Alkyl groups (prefix only)

🎨 The highest one becomes suffix; the rest become prefixes.

💠 4. Suffix Rules (When a Group Gets Priority)

✔ Choose longest chain containing the highest-priority group

✔ Number chain to give it the lowest number

✔ Add multiplicative prefixes when needed:

• di • tri • tetra

Examples:

• HOOC-CH₂-CH₂-OH → 3-hydroxypropanoic acid

• CH₃-CO-CH₂-NH₂ → 3-amino-2-propanone

🟪 5. Prefix Rules (For Lower Priority Groups)

When a group does not get the suffix position, its name changes to a prefix:

🌿 6. Choosing Parent Chain or Ring

✔ Must contain the highest-priority group

✔ Must contain maximum substituents

✔ For aromatic compounds, phenyl or benzenecarboxylic acid is used depending on priority

💡 7. Double & Triple Bonds

If present but not the highest priority:

• Named as -ene / -yne

• Position included

• Still must be part of the parent chain

Example:

HOOC-CH=CH-OH → 3-hydroxyprop-2-enoic acid

🧲 8. Naming Flow for Poly-Functional Compounds

Follow this easy sequence:

Pick highest-priority functional group

Choose parent chain containing it

Number chain to give lowest locant

Use suffix for main group

Use prefixes for others

List prefixes in alphabetical order

Assemble complete name

🧪 9. Ready-Made Examples

Example 1

HOOC-CH₂-CH₂-NH₂ 

→ 3-aminopropanoic acid

Example 2

CH₃-CH(OH)-CH₂-CHO 

→ 3-hydroxybutanal

Example 3

Br-CH₂-CH₂-COOH 

→ 3-bromopropanoic acid

🌟 10. Exam-Focused Golden Tips

💎 Always check priority table before naming

💎 Only one suffix for the parent compound

💎 Prefixes are alphabetised

💎 Avoid skipping carbons while numbering

💎 Give priority group the smallest possible number

💎 Ring systems follow same priority rules

🌈 🧪 MCQ Quiz (Advanced Level) on Poly-Functional Compounds 🧪

MCQ 1
What is the IUPAC name of HOOC–CH₂–CH₂–OH?
🟩 A. 3-Hydroxypropanoic acid
🟥 B. Propane-1-ol-3-oic acid
🟦 C. Hydroxypropanoate
🟨 D. 2-Hydroxypropanoic acid

---

MCQ 2
Identify the correct name for CH₃–CO–CH₂–NH₂.
🟩 A. 3-Aminopropanone
🟥 B. Aminoacetone
🟦 C. 2-Aminopropanone
🟨 D. 3-Amino-2-propanone

---

MCQ 3
Which functional group gets suffix priority?
🟩 A. Aldehyde
🟥 B. Amide
🟦 C. Ketone
🟨 D. Amine

---

MCQ 4
Name the compound: CH₃–CH(OH)–CH₂–CHO
🟩 A. 3-Hydroxybutanal
🟥 B. 2-Hydroxybutanal
🟦 C. 3-Hydroxybutanone
🟨 D. Hydroxypropanal

---

MCQ 5
Which prefix is used for a nitrile group when not main?
🟩 A. Cyano
🟥 B. Nitrilo
🟦 C. Nitroso
🟨 D. Carbamido

---

MCQ 6
CH₃–CH₂–COOH has which suffix?
🟩 A. –oic acid
🟥 B. –one
🟦 C. –al
🟨 D. –ol

---

MCQ 7
Name: HOOC–CH=CH–OH
🟩 A. 3-Hydroxyprop-2-enoic acid
🟥 B. Hydroxyacrylic acid
🟦 C. Propenoic hydroxy acid
🟨 D. Hydroxypropanoic acid

---

MCQ 8
Which group has highest priority?
🟩 A. Carboxylic acid
🟥 B. Alcohol
🟦 C. Ketone
🟨 D. Amine

---

MCQ 9
Prefix for aldehyde when not main group:
🟩 A. Formyl
🟥 B. Aldo
🟦 C. Oxo
🟨 D. Carboxy

---

MCQ 10
Name the compound: Br–CH₂–CH₂–COOH
🟩 A. 3-Bromopropanoic acid
🟥 B. Bromopropanoic acid
🟦 C. 2-Bromopropanoic acid
🟨 D. Bromomethanoic acid

---

MCQ 11
HOOC–C≡C–CH₂–NH₂ is named as:
🟩 A. 4-Aminobut-2-ynoic acid
🟥 B. Aminobutynoic acid
🟦 C. Aminobutyne acid
🟨 D. 2-Amino-4-ynoic acid

---

MCQ 12
Which group must get lowest locant?
🟩 A. Highest-priority functional group
🟥 B. Double bond
🟦 C. Longest substituent
🟨 D. Halogen group

---

MCQ 13
OH used as prefix becomes:
🟩 A. Hydroxy
🟥 B. Oxo
🟦 C. Hydroxyl
🟨 D. Oxy

---

MCQ 14
CHO used as prefix becomes:
🟩 A. Formyl
🟥 B. Oxo
🟦 C. Carboxy
🟨 D. Methanal-yl

---

MCQ 15
Choose correct name: CH₃–CH₂–CH₂–CO–CH₃
🟩 A. Pentan-2-one
🟥 B. Pentanone
🟦 C. 2-Pentanal
🟨 D. Butan-2-one

---

MCQ 16
Which is correct priority order?
🟩 A. Acid > Aldehyde > Alcohol > Amine
🟥 B. Alcohol > Acid > Ketone
🟦 C. Ketone > Amide > Acid
🟨 D. Aldehyde > Acid > Amide

---

MCQ 17
A compound with both –NH₂ and –OH:
🟩 A. OH gets suffix
🟥 B. NH₂ gets suffix
🟦 C. Both get suffix
🟨 D. Neither gets suffix

---

MCQ 18
Identify the correct name: HOOC–CH₂–CH(OH)–NH₂
🟩 A. 3-Hydroxy-2-aminopropanoic acid
🟥 B. Aminohydroxypropanoic acid
🟦 C. Hydroxyaminopropanoic acid
🟨 D. 2-Hydroxy-3-aminopropanoic acid

---

MCQ 19
Prefix for COOH when not main group:
🟩 A. Carboxy
🟥 B. Oicyl
🟦 C. Acidyl
🟨 D. Oxycarbon

---

MCQ 20
Which is correct?
🟩 A. Only one functional group gets suffix
🟥 B. Two groups may get suffix
🟦 C. All groups become suffix
🟨 D. Suffix is optional

---

MCQ 21
Which is written first among prefixes?
🟩 A. Alphabetically earliest
🟥 B. Highest priority
🟦 C. Longest chain
🟨 D. Halogens only

---

🎉 ANSWERS
1-A
2-D
3-B
4-A
5-A
6-A
7-A
8-A
9-A
10-A
11-A
12-A
13-A
14-A
15-A
16-A
17-A
18-A
19-A
20-A
21-A

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