IUPAC prefixes-suffixes for various compounds, Chemistry tutorial

IUPAC prefixes-suffixes for various compounds:

Let us now learn how diverse compounds having different functional groups are symbolized. In case of compounds that contain a functional group, the functional group obtains precedence over the alkyl substituent. At this point, we pass on back to Table where IUPAC prefixes and suffixes for several classes of compounds are following.

Alkenes: The suffix ane of the parent hydrocarbon is transformed to ene and the functional group (a double bond in this case) is following the lowest possible number. 

Some instances are: 

 CH2=CH           CH3CH=CH2

ethene                      propene

(Common name: ethylene)

 4       3      2      1                   1        2        3       4         5

CH3 CH2 CH=CH2                    CH3 - CH = CH - CH2 - CH3

but-l-ene                                                    pent-2-ene

Alkynes: In this case suffix ane of the parent hydrocarbon is changed to yne. Unsurprisingly, here as well the functional group is following the lowest number.

2223_4-methylpent-2-yne.jpg

Whenever together double and triple bonds are present, then the double bond obtains the lower number. Therefore, for the compound given below;

 1        2       3     4      5

CH2 = CH - CH2 - C ≡ CH

The correct name is pent - l-ene-4-yne 

Alkyl halides: The alkyl halides are the halogen derivatives of alkanes. The halogens present are generally F, Cl, Br and I. The ordinary names are arrived at via writing the name of alkyl group followed via the name of the halide. Illustrations are given below:

2377_alkyl halides.jpg

In the IUPAC system of nomenclature, prefix halo- (for that fluoro, chloro-bromo or iodo-) is utilized to provide the lowest number to the carbon atom to that the halogen is attached. For instance, several halogen compounds are named beneath:

837_2-chloro-5-methylhexane.jpg

Whenever more than one kind of halogen atoms is present, their names are arranged in alphabetical array as given in the next instance,

1094_5-bromo-1-chloro-2iodo-4-methylpentane.jpg

Alcohols: Alcohols are the compounds having hydroxyl (-OH) group connected to the alkyl chain. The ordinary names of the alcohols are written via identifying the alkyl group given as the word alcohol, for example

2459_alcohols.jpg

In the IUPAC nomenclature, suffix ol is utilized instead of final e of the parent hydrocarbon. The position of the hydroxyl group is following through assigning the lowest possible number to the carbon atom carrying it. Some instances are:

 Ethers: The ordinary names for ethers are originated via naming the 2 alkyl groups in alphabetical array followed via the word ether. This is illustrated in the instances given below:

 CH3OCH3                              CH3OCH2CH3

 dimethylether                    ethyl methyl ether

In the IUPAC system, ethers are symbolized as alkoxyalkanes. The larger of the 2 alkyl groups is chosen as the hydrocarbon chain. For instance, the compound,

      1                       2  

 CH3OCH2             CH3

Is symbolized as 1-methoxyethane and not as ethoxymethane. In the same way, the compound, has the name 1-ethoxy-2-methylpropane.

Aldehydes:  Lower members of this class are generally symbolized after the acids that they form on oxidation. For instance, HCHO, formaldehyde is named so since it forms formic acid (HCOOH) on oxidation.

In the IUPAC system of nomenclature, they are named as alkanals. The simplest aldehyde is methanol. Since the aldehyde group - CHO) is forever at the conclusion of the chain, it is always numbered as C - 1 in the chain, but this number is not specified in the name, for that the compound.

558_3,3-dimethylbutanal.jpg

Ketones: The ordinary names for ketones are written alike to ethers, such as the two alkyl groups are written alphabetically given through the word ketone. For instance, the compound,

         O

         ||

CH3 -C -CH2CH3

 is generally recognized as ethyl methyl ketone.

                                    O

                                    ||

Therefore, acetone, CH3CCH3 is as well recognized as dimethyl ketone. The IUPAC names for ketones are derived via using the suffix one instead of final e of the parent hydrocarbon. As normal, the location of the carbonyl group is point out through the lowest possible number. A few instances are,

92_ketons.jpg

Carboxylic acids: Nowhere also in organic chemistry, the ordinary names are as prevalent as they are among carboxylic acids. Several instances are listed in Table beside through both their ordinary and IUPAC names. For monocarboxylic acids,

                                                                O                                  

                                                                ||  

"For example acids having one carboxy (- C - OH) group", the IUPAC names are originated through replacing e ending of the alkane via oic acid. As for aldehydes, the carboxyl carbon is numbered 1. Though, in case of the dicarboxylic acids, the ending e of the hydrocarbon is not dropped.

Table: Some Carboxylic Acids

1119_Carboxylic Acids.jpg

Acyl halides: Acyl halides are usually symbolized through placing the names of the halide after the name of the acyl group. The acyl group is attained from the carboxylic acid via removal

                                                      O

                                                      ||

                                                      O

                                                      ||

of its hydroxyl portion, for that . R - C - OH guides to R-C- acyl group. The acyl group is named through using yl as the ending instead of ending icin the carboxylic acid. Several instances are:

2157_acetyl chloride.jpg

IUPAC names for acyl groups employ the ending oyl instead offending e in the name of the analogous hydrocarbon. The acetyl chloride has the IUPAC name  

ethanoyl chloride. Another example is

168_2-methylpropanoyl chloride.jpgwhich is symbolized as 2-methylpropanoyl chloride              

Acid amides: The ordinary names for acid amides are originated via replacing the suffix ic or oic of the carboxylic acid via the suffix amide as given below:

      O

      ||

CH3C - NH2

(acetic - acetamide)

The IUPAC name for an amide is derived via appending the suffix amide to the parent hydrocarbon by the final e dropped. Therefore, acetamide has the IUPAC name ethanamide. Having done this, can we give common and IUPAC names for

  O

  ||

HC - NH2  Such are formamide and methanamide, correspondingly.

Acid anhydrides: A symmetrical anhydride is named as anhydride of the parent    

                                  O        O

                                  ||        || 

acid. Therefore, CH3 - C - O - C - CH3, the anhydride that is attained from ethanic acid (common name: acetic acid) is generally recognized as acetic anhydride. The IUPAC name for this anhydride is ethanoic anhydride.

For mixed anhydrides, both the parent carboxylic acids are cited in alphabetical order, followed by the word anhydride, as illustrated below:

       O        O

       ||        ||

  H - C - O - C - CH3

Ethanoic methanoic anhydride (ordinary name: acetic formic anhydride)

Ethers: As the ethers contain alkyl and alkanoyl (acyl) groups, they are named as alkyl alkanoates. The alkyl group is cited 1st, followed through the name of the alkanoyl (acyl) portion which is symbolized via replacing the ic ending of the carboxylic acid by the suffix ate.

1836_ethers.jpg

Amines: There are 2 systems of naming amines. One process names them as alkylamines and the other terms them as alkanamines.  The alkanamine naming system was initiated through Chemical Abstracts and is easier to utilize as compared to the previous IUPAC system of alkylamine names. The most recent modification of IUPAC rules admits both systems and instances below are symbolized in both ways.  Bonding, Functional Group Classification and Nomenclature

562_Functional Group Classification.jpg

(Note that the numbering starts at the carbon and not at the nitrogen of the amine part). Primary diamines are symbolized via using the suffix diamine after the name of the hydrocarbon.

1224_1,4-butanediamine.jpg

For the secondary and the tertiary amines, the longest alkyl group present is considered as the parent chain. The remaining alkyl groups are symbolized as substituents connected to the nitrogen and a prefix N- is utilized by the name of the alkyl group.

1077_N-methylethanamine.jpg

Whenever utilized as a substituent, the -NH2 group is termed as amino and is prefixed by a number indicating the carbon atom to that it is attached.  

1261_N,N- dimethylaminoethanoic acid.jpg

Nitro compounds: The nitro compounds are named as nitro derivatives of the analogous hydrocarbons.

Examples being,

Nitriles:  Nitriles are named in the IUPAC system by using the suffix - nitrile to the name of the hydrocarbon corresponding to the longest carbon chain. Note that here the carbon of the nitrile group is included in the numbering of carbon chain and is numbered as position 1. Some examples are given below:

662_ethanenitrile.jpg

Whenever termed as a substituent, the -CH group is symbolized a cyano group. For instance, the compound.

         O

         ||

CH3 - C - OCH2CN is termed as cyanomethyl ethanoate.

Thiols: In naming thiols, an ending thiol is employed as a suffix to the name of the analogous hydrocarbon; for instance,

2419_ethanethiol.jpg

Sulphonic acids: The names of sulphonic acids use the suffix sulphonic acid by the name of the analogous hydrocarbon.

300_methanesulphonic acid.jpg

Until now, we have studied about the nomenclature of monofunctional compounds, for example the compounds that have only one functional group. In poly functional compounds were more than one functional groups are here, one group is  recognized as the principal functional group and this principal functional group is  utilized as a suffix in the name of the compound. The priorities for assortment of principal functional group are following below in the array of reducing precedence. The order is carboxylic acid, sulphonic acid, ester, acid anhydride, acyl halide, amide, nitrile, aldehyde, ketone, alcohol, thiol, amine, alkyne, alkene, ethers, halides, nitro.

 The order of priority for diverse functional groups is decided through considering the given points:

(i)  Functional groups that have an IUPAC suffix and end a carbon chain have .0 highest priorities, for example: carboxylic acids and their derivatives.

(ii)  Next are the groups that contain a suffix and can be located at any position in the molecule, for example: hydroxyl and amino groups.

(iii)  Groups having no suffix and that are termed as substituent, are following the lowest priority, instance being the halogens.

Let us learn the instances following below which demonstrate the nomenclature of polyfunctional compounds.

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