Q.Write the IUPAC names of the following amines :
a. CH3-CH2-N(CH3)-CH2-CH2-CH3
b. CH3-C(CH3)2-CH2-CH2-NH2
c. CH3-CH(CH3)-NH-CH2-CH3
(These three structures are printed in the source as stacked line-fragments -- a substituent group's formula on one line and its point of attachment on the line below -- and are reassembled here into standard linear notation.)

$(CH_3)_3C-NH_2$ (tert-butylamine) is named 2-methylpropan-2-amine by IUPAC rules.

To name an amine by IUPAC substitutive nomenclature, the longest carbon chain containing the carbon bearing the $-NH_2$ group is selected as the parent, and the suffix '-amine' is added with a locant, while other substituents are cited as prefixes with their own locants.

For $(CH_3)_3C-NH_2$: the central carbon carries three methyl groups and one $NH_2$ group. Taking one of the methyl groups as part of the main chain gives a 3-carbon parent chain, propane: $CH_3-C(CH_3)_2-NH_2$ can be numbered as $C_1H_3-C_2(CH_3)-C_3H_3$ with $NH_2$ on C-2 and an extra methyl substituent also on C-2 (numbering chosen to give the lowest locant to the principal characteristic group, the amine).

So the name is built as: 2-methyl (for the branch) + propan (3-C chain) + 2-amine (NH2 at C-2) = 2-Methylpropan-2-amine. This compound is commonly called tert-butylamine.

CH₂=CH–CH₂–NH–CH₃ is named as a propene chain bearing an amine at C1 and an N-methyl substituent, giving N-methylprop-2-en-1-amine.

Structure: CH₂=CH–CH₂–NH–CH₃

1. Identify the parent chain: the longest carbon chain containing the –NH– nitrogen's point of attachment is the 3-carbon allyl chain, CH₂=CH–CH₂–, which as a substituted amine is named as prop-2-en-1-amine (double bond between C2–C3, amine at C1).
2. The nitrogen carries an extra methyl substituent (–CH₃) instead of a second hydrogen, so this substituent is cited with the italic locant N- to show it is on nitrogen, not on the carbon chain: N-methyl.
3. Combine: N-methylprop-2-en-1-amine.

The other options are incorrect: 'Allylmethylamine' is only an acceptable common/trivial name, not IUPAC; 'amino-pentene' and 'aminopent-1-ene' wrongly assume a 5-carbon chain, but the molecule has only 3 carbons in its main chain plus the separate N-methyl group.

N,N-dimethylethanamine: $CH_3CH_2-N(CH_3)_2$ (both N-H's of ethanamine replaced by methyl groups).

'Ethanamine' is the IUPAC name for ethylamine, $CH_3CH_2-NH_2$. The prefix 'N,N-dimethyl' means two methyl groups replace the two hydrogens on the nitrogen atom itself:

$CH_3CH_2-N(CH_3)_2$

This is N,N-dimethylethanamine (also called N,N-dimethylethylamine), a tertiary amine.

Name the longest carbon chain bearing the -NH- group as the parent "...amine", and cite the second alkyl group on nitrogen with an italic N- locant.

Structure: CH$_3$–CH(CH$_3$)–NH–CH$_3$, i.e. (CH$_3$)$_2$CH–NH–CH$_3$ — this is a secondary amine: an isopropyl group and a methyl group both attached to the same nitrogen.

IUPAC naming for secondary/tertiary amines:

1. Identify the parent chain carrying the nitrogen with the longest carbon skeleton directly bonded to N: here that's the 3-carbon isopropyl fragment, CH$_3$–CH(NH...)–CH$_3$, named as propan-2-amine (amine group on C-2 of propane).
2. The second substituent on nitrogen (the extra CH$_3$) is cited as an N-methyl prefix (locant "N" shows it's on the nitrogen, not on a ring/chain carbon).

Combining: N-methylpropan-2-amine.

(Options (c) and (d) wrongly use a 4-carbon "butanamine" parent, which doesn't match this 3-carbon + N-methyl structure; option (b) drops the C-2 locant needed since the amine isn't terminal.)

CH3-CH(NH2)-CH3 is a 3-carbon chain with -NH2 on C2 → propan-2-amine.

The compound CH3-CH(NH2)-CH3 has a parent chain of three carbons (propane) with an amino group -NH2 on the central carbon (position 2). The IUPAC name is formed as propan-2-amine (the -e of propane is dropped before -amine). Its common name is isopropylamine, but the IUPAC name asked for is propan-2-amine.

The longest carbon chain attached to N (ethyl, 2 carbons) is chosen as the parent 'ethanamine'; the two remaining methyl groups on N are cited as N,N-dimethyl substituents.

C₂H₅–N(CH₃)–CH₃ is a tertiary amine with three groups on nitrogen: one ethyl and two methyl groups. IUPAC naming of amines picks the longest carbon chain bonded to the nitrogen as the parent chain (here, the 2-carbon ethyl group, giving the parent 'ethanamine'), and cites every other group attached to N with the locant 'N-', since N is not part of the numbered carbon chain. The two extra methyl groups on nitrogen are therefore cited together as 'N,N-dimethyl'.

Pick the longest carbon chain running through the carbon attached to nitrogen, number to give the amine (and thus the N-substituent carbon) the lowest locant, and cite the branch and the two N-methyls as substituents.

The amine nitrogen is bonded to two methyl groups and to a carbon (call it C*) that itself carries: a methyl group, an ethyl group, and continues into a -CH₂-CH₃ chain.

To find the parent chain, take the longest carbon chain running through C* (the carbon bearing the amino group): combining the ethyl branch on one side with the -CH₂-CH₃ continuation on the other side through C* gives a 5-carbon chain (pentane): $CH_3-CH_2-C^*(CH_3)(NMe_2)-CH_2-CH_3$, with C* as carbon 3 of that chain (the methyl group on C* becomes a 3-methyl substituent, and the shorter methyl-only branch is not chosen as it would give a shorter parent chain).

• Parent chain: pentane, amine at C3 → pentan-3-amine.
• Substituents: two methyl groups on the amine nitrogen → N,N-dimethyl; one methyl group on C3 of the chain → 3-methyl.

Name: 3-Methyl-N,N-dimethylpentan-3-amine.

CH3–CH(NH2)–CH2–CHO is a 4-carbon chain named as a butanal with an amino substituent, giving 3-aminobutanal.

Since the aldehyde group (–CHO) is the senior (principal) characteristic group, the chain is numbered from the CHO carbon as C1: C1(CHO)–C2(CH2)–C3(CH–NH2)–C4(CH3). The parent chain is butanal (4 carbons), with the amino group as a substituent prefix 'amino' located at C3.

The nitrogen carries two ethyl groups and one propyl group attached through its terminal (C1) carbon, giving N,N-diethylpropan-1-amine (written N,N-diethylpropanamine).

C2H5–N(C2H5)–CH2CH2CH3 is a tertiary amine. The longest chain attached to N through a single bond at its end carbon is propyl (3 carbons), so the parent name is propanamine (locant 1 is the default/implied position since the amine is on the terminal carbon). The other two ethyl groups on N are cited as N,N-diethyl substituents.

Number the 3-carbon allyl chain from the end bearing the $-NH-$ group; the double bond is at C2–C3.

The compound is $CH_2{=}CH{-}CH_2{-}NH{-}CH_3$. The parent chain is the 3-carbon chain carrying the principal characteristic group ($-NH-$), i.e. propene: $C1(H_2N\text{-attached})-C2{=}C3$. Numbering to give the amine-bearing carbon the lowest locant: C1 bears the $NHCH_3$ group, and the double bond runs between C2 and C3, so the parent is prop-2-en-1-amine. The extra methyl group on nitrogen is indicated by the italic locant N: N-methyl.

Putting it together: N-methylprop-2-en-1-amine. (Options (c) and (d) wrongly number a but-1-ene/pent-1-ene chain instead of the correct 3-carbon propene chain with the amine as suffix.)