Q.Write IUPAC names of the following compounds:

Step-by-step

1. CH3-CH(CH3)-CH(OH)-C(CH3)2-CH3: five-carbon chain with -OH at C-3. Numbering from the C(CH3)2 end gives two methyls at C-2 and one at C-4, so it is 2,2,4-trimethylpentan-3-ol.
2. A seven-carbon chain (heptane) bearing -OH at C-2 and C-4 (a 2,4-diol) with an ethyl branch at C-5, so it is 5-ethylheptane-2,4-diol.
3. Four-carbon chain with -OH on C-2 and C-3, so it is butane-2,3-diol.
4. Three-carbon chain with -OH on all three carbons, so it is propane-1,2,3-triol (glycerol).
5. Phenol with a methyl ortho to -OH: 2-methylphenol. (vi) Methyl para to -OH: 4-methylphenol.

(vii) -OH at C-1 with methyls at C-2 and C-5 (the lowest locant set for this pattern): 2,5-dimethylphenol.

(viii) -OH at C-1 flanked by a methyl on each adjacent carbon: 2,6-dimethylphenol.

(ix) CH3-O-CH2-CH(CH3)-CH3: the larger group is the four-carbon 2-methylpropane; methoxy sits on C-1, so it is 1-methoxy-2-methylpropane.

(x) C6H5-O-C2H5: ethoxy on benzene, so it is ethoxybenzene (phenetole).

(xi) C6H5-O-(CH2)6CH3: a heptyl group on a phenoxy oxygen; named with the ring as a phenoxy prefix on heptane, so it is 1-phenoxyheptane.

(xii) CH3CH2-O-CH(CH3)CH2CH3: the larger group is butan-2-yl (a four-carbon chain), so ethoxy sits on C-2, giving 2-ethoxybutane.

Method: Comprehensive Principal-Group Nomenclature Method (Alcohols, Diols, Triols, Phenols, Ethers)

Core Concept

Every name is built the same way: find the correct parent (longest -OH-bearing chain for alcohols/diols/triols, the ring itself for phenols, the larger alkyl/aryl group for ethers), then number to give the principal group(s) the lowest possible locant(s), and cite every other substituent as an alphabetised prefix.

Steps

1. Classify the compound: does -OH sit on a chain carbon (alcohol/diol/triol) or directly on an aromatic ring (phenol)? Or is the functional group an ether linkage (-O- between two carbon groups, no H on that oxygen)?
2. For alcohols/diols/triols: find the longest chain through ALL -OH-bearing carbons; number from the end giving the lowest locant SET to the -OH groups; name remaining alkyl branches as prefixes.
3. For phenols: -OH fixes ring position 1; number substituents around the ring to give the lowest locant set (checking both directions of numbering).
4. For ethers: identify the two groups on oxygen; keep the larger as parent (chain, ring, or in special cases an alkyl chain even against an aryl group per the convention used), name the smaller as an alkoxy or phenoxy/aryloxy prefix, and number for the lowest locant on the parent.
5. Assemble each final name and double-check the locant set is truly the lowest possible by testing numbering from both ends/directions.

Applying this across all twelve parts: (i) 2,2,4-trimethylpentan-3-ol (five-carbon chain, -OH at C-3, two methyls at C-2, one at C-4).

(ii) 5-ethylheptane-2,4-diol (seven-carbon chain, -OH at C-2 and C-4, ethyl at C-5).

(iii) butane-2,3-diol (four-carbon chain, -OH at C-2 and C-3).

(iv) propane-1,2,3-triol (three -OH on three carbons = glycerol).

(v) 2-methylphenol (methyl ortho to -OH).

(vi) 4-methylphenol (methyl para to -OH).

(vii) 2,5-dimethylphenol (methyls at C-2 and C-5 relative to -OH at C-1).

(viii) 2,6-dimethylphenol (methyls flanking -OH on both sides).

(ix) 1-methoxy-2-methylpropane (larger 2-methylpropane parent, methoxy at C-1).

(x) ethoxybenzene (benzene parent, ethoxy substituent).

(xi) 1-phenoxyheptane (heptane parent since the alkyl chain is longer/named as parent with phenoxy prefix).

(xii) 2-ethoxybutane (larger butan-2-yl parent, ethoxy at C-2).

Key Exam Point

With this many parts in one question, the most common scoring loss is a SINGLE wrong locant from numbering the chain/ring from the wrong end (e.g., writing 3,4-dimethylphenol instead of 2,5- for part vii) — always explicitly compare both numbering directions before finalising each name, rather than numbering by inspection alone.