Suffixes naming aldehydes

The common method of naming aldehydes corresponds very closely to that of the related acids (see Carboxylic acids), in that the term aldehyde is added to the base name of the acid. For example, formaldehyde (qv) comes from formic acid, acetaldehyde (qv) from acetic acid, and butyraldehyde (qv) from butyric acid. If the compound contains more than two aldehyde groups, or is cycHc, the name is formed using carbaldehyde to indicate the functionaUty. The lUPAC system of aldehyde nomenclature drops the final e from the name of the parent acycHc hydrocarbon and adds al If two aldehyde functional groups are present, the suffix -dialis used. The prefix formjlis used with polyfunctional compounds. Examples of nomenclature types are shown in Table 1. 

The first step is to identify the parent function, which usually is determined from the suffix or word at the end of the name. Suppose, for example, that a structure is to be written for a compound having the name 3-methoxy-butanal. The suffix -al is the IUPAC suffix for aldehyde therefore the compound is an aldehyde and the function is —CHO. 

The IUPAC rules for naming aldehydes append the suffix -al to the parent name. The aldehyde carbon is always the first carbon in the chain, so a locant is not necessary. The simplest aldehyde, methanal, is commonly known as formaldehyde, a highly toxic gas used to preserve biological specimens. Ethanal is the next aldehyde, although most organic chemists call it acetaldehyde. 2,2,2-Tri-chloroethanal, more commonly known as chloral, reacts with water to form the sedative chloral hydrate. Phenylmethanal, more commonly known as benzalde-hyde, is used as artificial cherry or almond flavoring. Nomenclature examples of aldehydes are shown in Figure 11.34. 

Chlorocyclopentanecarboxylic acid (In similar fashion to the use of the -carbaldehyde suffix in naming aldehydes, cyclic compounds with the carboxy group attached to the ring use the name of the ring with the suffix -carboxylic acid.)... 

Name the highest priority functional group with a suffix (acid > aldehyde > ketone > alcohol > amine) and the others with prefixes. 

The rules for naming ketones in the I.U.P.A.C. Nomenclature System are directly analogous to those for naming aldehydes. In ketones, however, the -e ending of the parent alkane is replaced with the -one suffix of the ketone family, and the location of the carbonyl carbon is indicated with a number. The longest carbon chain is numbered to give the carbonyl carbon the lowest possible number. For example. 

Aldehydes are the class of carbonyl compounds where one substituent is an alkyl, alkenyl, or aryl group, and the other is a hydrogen atom, 4.34. The suffix for aldehydes is -al added to the hydrocarbon skeleton name, so if R = CH3, 4.34 would be ethanal (the old name, which is still commonly used, was acetaldehyde). In formal nomenclature, the aldehyde carbon is designated as C-1. When R = H, the name is methanal, but this compound is almost invariably known by its common name, formaldehyde. With more complex structures, the longest chain starting at C-1 is discerned, numbered, and the substituents put in as usual. So 4.35 is 2,3-dimethylpentanal. 

CH3CHO + [O] CH3COOH The systematic method of naming aldehydes is to use the suffix -al with the... 

Aldehydes. When the group —C(=0)H, usually written —CHO, is attached to carbon at one (or both) end(s) of a linear acyclic chain the name is formed by adding the suffix -al (or -dial) to the name of the hydrocarbon containing the same number of carbon atoms. Examples are butanal for CHjCHjCHjCHO and propanedial for, OHCCH CHO. 

When the aldehyde group is directly attached to a carbon atom of a ring system, the suffix -carbaldehyde is added to the name of the ring system, e.g., 2-naphthalenecarbaldehyde. When the aldehyde group is separated from the ring by a chain of carbon atoms, the compound is named (1) as a derivative of the acyclic system or (2) by conjunctive nomenclature, for example, (1) (2-naphthyl)propionaldehyde or (2) 2-naphthalenepropionaldehyde. 

Among oxygen containing groups, a higher oxidation state takes precedence over a lower one in deter-rnining the suffix of the substitutive nane. Thus, a compound that contains both an alcohol and an aldehyde function is named as an aldehyde. 

The aldehyde signature, -C-H (written also as -CHO, but never -COH), is always located at the end of the carbon chain. Common names for aldehydes are derived from the corresponding acid to which they are converted by further oxidation. The suffix ic acid is simply changed to -aldehyde ... 

The carbonyl group in glucose and ribose is an aldehyde such compounds are termed aldoses. Fructose, by contrast, has a ketone group and is therefore classified as a ketose. Glucose could also be termed an aldohexose and fructose a ketohexose, whereas ribose would be an aldopentose, names which indicate both the number of carbons and the nature of the carbonyl group. Another aspeet of nomenclature is the use of the suffix -ulose to indicate a ketose. Fructose could thus be referred to as a hexulose, though we are more likely to see this suffix in the names of specific sugars, e.g. ribulose is a ketose isomer of the aldose ribose. 

Common names replace the suffix -ic (-oic or -oxylic) and the word acid of the corresponding carboxylic acids by -aldehyde. Locations of substituents on chains are designated by Greek letters ... 

The suffix -al is appended to the name of the hydrocarbon corresponding to the longest carbon chain that includes the aldehyde carbon. Remember that alkane- + -al becomes alkanal with the e omitted, and because the al function is necessarily at Cl, the -1- is redundant and is omitted ... 

The simplest aldehyde is methanal, HCHO, which is familiarly known as formaldehyde. However, when aldehydes are named as derivatives of methanal, they usually are called carbaldehydes, and the suffix carbalde-hyde refers to the —CHO group. This system is used where the hydrocarbon group is not a chain, but a ring, and the CHO group can be thought of as a one-carbon chain ... 

The anomalous al suffix used in the trivial names of members of the family in all probability originated at the very beginning of their history from aldehydic impurities present in the original preparations in Emil Fischer s laboratory (see Section II.2.d.i). Compound 4, the D-glucose... 

Ans. (a) The longest chain is four carbons. The correct name is 2-butanol. (b) Such a compound is impossible because it would require five bonds on the third carbon, (c) Positions 1 and 4 are equivalent to 1 and 2. The correct name is 1,2-dichlorocyclobutane. (d) Such a compound is not possible because the aldehyde carbon must be at the end of the chain, (e) Such a compound won t work because it would require five bonds on the second carbon. (f) The suffix acid should be a separate word. The correct name is pentanoic acid. 

C The COOH group means that the molecule is a carboxylic acid and its name will use the suffix -oic acid. The presence of 4 carbon atoms means the prefix butan- will be used. An alternate name for the molecule is butyric acid. Choices A and B would be used for aldehydes (CHO group). Choices B and D would be used for 3 carbon atoms ... 

Common names for simple aldehydes are frequently encountered. These common names are derived from the common names for the related carboxylic acid (see Section 12.4) by replacing the suffix -ic acid with the suffix -aldehyde. Thus, the aldehyde related to acetic acid is acetaldehyde. If the carbonyl group of an aldehyde is attached to a ring system, the compound can be named as a hydrocarbon with the suffix -carbaldehyde. (Some sources use -carboxaldehyde.)... 

Aldehydes contain a carbonyl group (C=0) to which at least one hydrogen atom is attached. The suffix -al is placed on the end of the name of aldehydes. For example, the molecule CH3CH2COH is known as propanal. Aldehydes must have the carbonyl on the last carbon on the chain (in order to have the hydrogen atom attached to the carbon). As a result, there is no need for the use of numbers to distinguish the position of the carbonyl group. 

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