Question

) Correct name for this molecule Choose the correct name for the molecule @ 2- pentane ® 3-pentane ©2-pentene @3-pentene | Choose the correct name for this molecule OH сна- сH - сна- сно @ 2-hydroxa putanal 1,3-dihydroxy butanal © 3-hydroxybutanal Choose the correct name for the molecule Br u 2-methyl-4-bromo he xane Ⓡ4 bromo-2-methyl hexanone 4-bromo-2-methylhexane (CH3)₂N @ trimethylamine Ⓡa-aminopropane © 1,2,3-trimethylamine @a-propylamine 6 Choose the correct name of the molecule CH₃ C = C CH3 @ 2- butene ③ butyne © butene D 2-butyne

Answer 1

For nomenclature :

(a) look for presence of functional groups - anything apart from the standard C-H bonds. If there is more than one functional group, then the one which has higher priority according to IUPAC is chosen as the functional group.

(b) find and number the longest carbon chain, and give the lowest possible number to the functional group. Eg, In this way, if the carbon chain has 5 carbon, then the parent alkane name is pentane. The parent name then gets modified to accommodate the functional group. So, if the functional group is a carboxylic acid , eg : -COOH, then the parent compound is called pentanoic acid. If the - COOH is at carbon 1, then no further modification is needed. If it is on some other Carbon, ( say, 2) , then 2 is added before the parent compound ; 2 - pentanoic acid.

(c) while numbering, there may be substitutions on other carbons. These substitutions are mentioned before the parent compound, following the general format of : ( position number) - ( substitution) .

(d) while numbering the carbon chain, ensure that the Subsitutions get lowest possible number, after the functional group.

Some other points relevant here :

For numbering functional groups which include a C ( eg: Carboxylic acid, aldehyde, ketone etc) the C of the functional group is included in the numbering of parent chain

Halogens are not functional groups.

Solving:

2 2 Functional group double bond Numbering the longest chain, and trying to give double bond lowest number : (2 is is the lowest possible) 5 pentane . alkane = so, parent Considering functional group -penten 3 5 Carbon 2 OH 3 7 Сн,- CH-CH₂-CHO CHO -OH Functional group: Caldehyde), Calcohol Gets preference Numbering! •4 carbon = butane "Adding functional group: butanal Substitution of - OH at Carbon 3i | 3-hydrony butanal OH CH - CHO CH 3 -CH 3 2 4 2

Br o no separate functional group Chalogens are not considered as functional group [ remember, lowest possible numbers for substitutions] p). Numbering! n CH3 Br - Parent alkane = = 6 carbon =hexane. 6 4 2 3 A Adding substitutions Calphabetical order): 4- bromo 2-methyl hexane.

5 CH N. - CH3 3 the on CH3 (CH3)₂N Amine. (-NH2) Functional group Here, 3 CH3 groups (methyl groups) are substituted on the functional group. So, the (N,N,N) (trimethyl Camine Position of substitution Parent compound. The (N,N,N) is unnecessary, is amine, only name is K Since the which can parent compound have three substitutions Hence, name is a trimethylamine

6) CHz-e3c-CHE Functional group: Alkyne (triple bond) Numbe bering CH₃ -CEC- CH3 2 3 4 => [ 2- butyne