Nomenclature of Organic Compounds


Nomenclature of Organic Compoundspubs.acs.org/doi/pdf/10.1021/ba-1974-0126.ch026Similargroups, (2) highest degree of uns...

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Ethers

Compounds having the structure ROR', where R and R' are the same or different acyclic or cyclic groups, are called ethers. This class also includes cyclic structures in which one or more oxygen atoms are members of a ring, although such compounds are usually named as heterocyclic systems. Conceptually, the ether function may be regarded as having been derived by replacement of the hydrogen atom of the OH group in an alcohol or phenol with a hydrocarbon or heterocyclic group. Thus the term partial ether denotes a modified polyol structure in which some but not all of the OH groups have been converted to OR. From another viewpoint an ether group is produced when an oxygen atom replaces a C H group in a hydrocarbon chain or ring. Hence, the prefix oxa as used in replacement nomenclature denotes the ether function in the same manner in which the prefix oxy does in substitutive nomenclature. 2

Naming of sulfur analogs of ethers, which are called sulfides, is discussed in Chapter 39, Acetals, which constitute a subclass of ethers derived from aldehydes and ketones, are treated in Chapter 20.

Recommended Nomenclature Practice Acyclic ethers having no more than two —O— linkages within a single straight chain otherwise composed of carbon atoms are preferably named substitutively as oxy derivatives of one of the all-carbon chains present in the molecule. The parent (senior) chain is selected by applying the following criteria in the order listed: (1) largest number of attached OR groups, (2) highest degree of unsaturation, (3) longest chain, and (4) lowest locants for attached OR groups (see 1965 IUPAC Rule C-13.1). Names for acyclic OR groups are formed systematically by combining the prefix name of the R group with oxy—e.g., hexyloxy—but the shortened form alkoxy is preferred when the alkyl group contains less than five carbon atoms (Table 26.1). 202 In Nomenclature of Organic Compounds; Fletcher, J., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.

26.

Ethers

203

Table 26.1.Contractions of Names for Acyclic OR Groups

CH3O-

Methoxy

CH3CH2O-

Ethoxy Propoxy

CH CH CH 03

2

2

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CH3CH2CH2CH2O

CH

Butoxy

-

3

I

Isopropoxy*

CH3CHO-

CH

3

fl

Isobutoxy

CH CHCH 03

2

CH

3

I

fl

sec-Butoxy

CH CH CHO3

2

CH

3

I

a

tert-Butoxy

CH3CO-

CH a

3

For the unsubstituted group only.

As alternatives to substitutive names for acyclic monoethers of symmetrical structure, radicofunctional names terminating in the word ether may be used. CH OCH CH CH CH 3

2

2

2

1-Methoxybutane

3

CH OCH CH OCH CH CH 3

2

2

2

CH

I

2

Isobutoxyethene

2

CH CH 3

3

3

CH CH CHOCHCH CH 3

2

l-Methoxy-2-propoxy ethane

3

CH =CHOCH CHCH 2

3

2

3

2-s^c-Butoxybutane Di-5^c-butyl ether

In Nomenclature of Organic Compounds; Fletcher, J., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.

204

N O M E N C L A T U R E O F ORGANIC

OCH

3

1,2,3-Trimethoxypropane

CH OCH CHCH OCH3 3

COMPOUNDS

2

2

Acyclic polyethers having more than two —O— linkages within a single straight chain are best named by using replacement nomenclature (see Chapter 7). CH OCH CH OCH CH OCH CH Downloaded by PENNSYLVANIA STATE UNIV on February 25, 2013 | http://pubs.acs.org Publication Date: June 1, 1974 | doi: 10.1021/ba-1974-0126.ch026

3

2

2

2

2

2

3

2,5,8-Trioxadecane

Cyclic ethers having one or more —O— linkages connecting two ring systems are preferably named substitutively as oxy derivatives of the senior ring system carrying the most OR groups. In choosing the senior ring system as the parent compound, all heterocycles are preferred to all carbocycles, and nitrogen-containing heterocycles are preferred to those not containing nitrogen. If no heterocyclic system is present, the senior carbocyclic system containing the largest number of OR groups is selected as the parent compound. (For more detailed information on seniority of ring systems, see 1965 IUPAC Rule C-14.1 and the Introduction to the Subject Index, Chem. Abstr. 1967, 66, 1 29-33). Names of cyclic OR groups are formed systematically by combining the prefix name of the R group with oxy—e.g. - cyclohexyloxy—except that the contraction phenoxy is preferred for C H O — . For symmetrical cyclic monoethers, radicofunctional names ending with the word ether are acceptable alternatives to the preferred substitutive names. t

6

s

2-(2-Naphthyloxy)naphthalene Di-2-naphthyl ether

3-(Oxacyclohex-3-yloxy)oxacyclohexane Bis(tetrahydropyran-3-yl) ether

(Cyclopentyloxy)benzene

1,4-Diphenoxybenzene

In Nomenclature of Organic Compounds; Fletcher, J., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.

26. Ethers

205 H

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2-(2-Anthryloxy)azacyclopentane

Cyclic-acyclic monoethers are preferably named substitutively as oxy derivatives of the senior ring or chain present. When there is a choice, all heterocyclic systems are preferred to all cyclic and acyclic hydrocarbon systems; otherwise the largest hydrocarbon is selected as the parent. Symmetrical structures may also be named radicofunctionally.

Propoxybenzene

2-(4-Methoxyphenyl)naphthalene

2-(2-Cyclohexylethoxy)thiacyclopentane

CH OCH 2

2

l-(l-Naphthylmethoxymethyl)naphthalene Bis(l-naphthylmethyl) ether

CH2CH3

3- [(Cy clopentyloxy )methyl] heptane

Cyclic-acyclic polyethers are named similarly, except that in selecting the parent chain or ring system consideration is first given to the number of attached O R groups.

In Nomenclature of Organic Compounds; Fletcher, J., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.

206

NOMENCLATURE OF ORGANIC COMPOUNDS

^

^—OCH CH 0—^ 2

CH Q—i^^—Q—^

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1,2-Diphenoxyethane

^ _ Q C H

3

OCH

^

2

3

l,3-Dimethoxy-5-(4-methoxyphenoxy)benzene

3

Straight chains containing more than two —O— linkages are best named by using replacement nomenclature (see Chapter 7).

)—i CH3O—^

\—OCH CH OCH CH OCH CH OCH CH 0—/ 2

2

2

2

2

2

2

2

J—OCH CH OCH CH OCH CH OCH CH 0—^ 2

2

2

2

2

2

2

2

\ — ^—OCH

3

1,1 l-Bis(4-methoxyphenoxy)-3,6,9-trioxaundecane Structures that contain one or more —O— linkages in a ring system are preferably named as heterocyclic compounds (see Chapter 6).

4H-l-Oxaanthracene

1,4,5,8-Tetraoxanaphthalene

As an alternative to the regularly formed heterocycle names for structures in which O is attached to two adjacent carbon atoms of a chain or ring, the bivalent substitutive prefix epoxy may be used.

CH3CHCHCOOH

\j

3-Methyloxacyclopropane-2-carboxylic acid 2,3-Epoxybutanoic acid

The term epoxy is also used as a nondetachable prefix (see Chapter 6, discussion section) in naming bridged polycyclic aromatic structures.

In Nomenclature of Organic Compounds; Fletcher, J., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.

207

26. Ethers

9,10-Dihy dro-9,10-epoxy an thracene

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Discussion The word ether is properly used only as a generic term denoting a functional class of compounds; it should never be used in place of diethyl ether as a specific name for the compound C H 3 C H 2 O C H 2 C H 3 . Since, in substitutive nomenclature, the ether function is always cited as a prefix, it is not considered i n selecting the principal function when naming compounds of mixed functions substitutively (see Chapter 10). For this reason, the ether function does not appear in the second part o l Table 8.1; it is included, however, by both I U P A C and Chemical Abstracts in their order-of-precedence listings, which apply not only to substitutive but also to radicofunctional nomenclature. Although radicofunctional names are still widely used in naming ethers, notably by Chemical Abstracts until 1972, substitutive nomen­ clature is preferred for reasons of systematization. However, for sym­ metrical monoethers, particularly those of simple structure, the more familiar radicofunctional names ending in the word ether (not oxide) are acceptable second choices. Although Chemical Abstracts has indexed simple symmetrical ethers under names such as " E t h y l ether" for diethyl ether and "Phenyl ether" for diphenyl ether, omission of the prefix di or bis is incorrect by modern principles of organic nomenclature and should be avoided. Additive names such as "ethylene oxide" and "styrene oxide" should be abandoned in favor o f the systematic names oxirane and phenyloxirane. As noted in Chapter 7, replacement nomenclature offers a convenient, systematic means of naming acyclic ethers, particularly when more than two —O— linkages occur within a single straight chain. Although replacement names have been officially recommended and used only for polyethers of relatively complex structure, names such as oxapropane for CH3OCH3 and 2,5-dioxahexane for C H O C H C H O C H are certainly acceptable. Partial ethers o f polyhydroxy compounds are best named substitutive­ ly as oxy derivatives of the appropriate alcohol or phenol (see Chapters 19 and 35). Names such as "diethylene glycol" for H O C H C H O C H C H O H and "ethylene glycol monoethyl ether" for C H C H O C H C H O H should be abandoned in favor of 2,2'-oxydiethanol and 2-ethoxyethanol, respec­ tively; likewise, names such as 1-O-methylresorcinol are not recom­ mended, although this type of name is used in specialized nomenclature of carbohydrates (see Chapter 30). 3

2

2

3

2

3

2

2

2

2

2

In Nomenclature of Organic Compounds; Fletcher, J., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.

2

208

NOMENCLATURE OF ORGANIC COMPOUNDS

A few trivial names for ethers are recognized in the 1965 IUPAC Rules (see Examples 10,11,13,14,15 and 16) but these are falling into disuse and should be abandoned.

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Table 26.2. Examples Of Acceptable Usage 1.

CH3OCH3

2.

CH3CH OCH CH2Br

l-Bromo-2-ethoxyethane

3.

C1CH 2 CH 2 OCH 2 CH 2 CI

l-Chloro-2-(2-chloroethoxy)ethane

2

Methoxymethane Dimethyl ether not Methyl ether 2

Bis(2-chloroethyl) ether CH OCH2CH CH20CH

4.

3

2

1,3 -Dimethoxy propane

3

5.

CH CH(OCH2CH CH2CH2CH )2

l,l-Bis(pentyloxy)ethane

6.

CH3OCH2OCH2CH2OCH2OCH3

2,4,7,9-Tetraoxadecane

2

3

a

3

fi ^ O—/ \ \

Phenoxybenzene Diphenyl ether

/

not Phenyl ether 2-( 1,8-Diazanaphth-2-yloxy )-l ,8diazanaphthalene Di-l,8-naphthyridin-2-yl ether

2-(2-Naphthyloxy)thiacyclopentane Tetrahydro-2-(2-naphthyloxy)thiophene 10. £H Q / 3 — \

\ //

Methoxybenzene not Anisole

11. CH3CH2O—\

\ 12.

\

/

Ethoxybenzene not Phenetole

N |J—OCH=CH l|

2

2-(Ethenyloxy)azabenzene 2-(Vinyloxy)pyridine

In Nomenclature of Organic Compounds; Fletcher, J., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.

26.

Ethers

209

CH O — ^

^—CH=CHCH

3

3

l-Methoxy-4-( l-propenyl)benzene not Anethole 14.

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2-Methoxybenzenol 2-Methoxyphenol not Guaiacol

1,2-Dimethoxybenzene not Veratrole

2-Methoxy-4-(2-propenyl)benzenol 4-Allyl-2-methoxyphenol not Eugenol

17. \

y

\

/

(Phenylmethoxymethyl)benzene Dibenzyl ether not Benzyl ether

18. \ / O

19.

\

/ \ = /

CH CHCH C1 \ / O 2

2

t

no

l,2-Epoxy-l,2-diphenylethane Stilbene oxide

(Chloromethyl)oxirane l-Chloro-2,3 -epoxy propane not Epichlorohydrin

20.

2-(Phenoxymethyl)oxacyclopenta-2,4-diene 2-(Phenoxymethyl)furan

In Nomenclature of Organic Compounds; Fletcher, J., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.

N O M E N C L A T U R E O F ORGANIC C O M P O U N D S O L

/

C H

/

3

CH

~ O

3 3

2,2-Dimethy 1-1,3 -dioxacy clopentane 2,2-Dimethy 1-1,3-dioxolane

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Oxacyclohexa-2,5-diene 4H-Pyran

1,4-Dihydro-l ,4-epoxynaphthalene

HOCH CH OCH CH OH 2

2

2

2,2'-Oxydiethanol not Diethylene glycol

2

HOCH CH OCH CH OCH CH OH 2

2

2

2

2

2

2,2'-(Ethylenedioxy)diethanol not Triethylene glycol CH CH OCH CH OH 3

2

2

2-Ethoxyethanol not Ethylene glycol monoethyl ether

2

H NCH CH OCH CH NF 2

2

2

2

2

V-o—f

ci—f

2,2'-Oxydiethanamine 2,2'-Oxybis(ethylamine)

2

V-ci l-Chloro-4-(4-chlorophenoxy)benzene Bis(4-chlorophenyl) ether

HO—/ N^

\—0—/ / \

\ — O H 4,4'-Oxydibenzenol / 4,4'-Oxydiphenol

HOOCCH 0—l^^—OCH COOH 2

2

C

*

CH C(OCH CH ) 3

3

z

2

a

3 a

(4-Chloro-l,3-phenylenedioxy)diethanoic acid (4-Chloro-l,3-phenylenedioxy)diacetic acid 3

1,1,1-Triethoxyethane not Tnethyl orthoacetate

In Nomenclature of Organic Compounds; Fletcher, J., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.