Aromatic series

Secondary amines of both the aliphatic and the aromatic series react similarly with nitrous acid, giving nilrosamines ... 

This group comprises substances of the tjrpe RCONHR and RCONR R", i.e., substituted amides of the aromatic series. They are all well-defined crystalline sohds, sparingly soluble in cold but, often, appreciably soluble hi hot water and moderately soluble in ether they are generally neutral or feebly basic in reaction. 

Oximes, hydrazines and semicarbazones. The hydrolysis products of these compounds, t.e., aldehydes and ketones, may be sensitive to alkali (this is particularly so for aldehydes) it is best, therefore, to conduct the hydrolysis with strong mineral acid. After hydrolysis the aldehyde or ketone may be isolated by distillation with steam, extraction with ether or, if a solid, by filtration, and then identified. The acid solution may be examined for hydroxylamine or hydrazine or semicarbazide substituted hydrazines of the aromatic series are precipitated as oils or solids upon the addition of alkali. 

The procedures as outlined are applicable to both the aliphatic and aromatic series. They are superior to the common interchange method in that they avoid the fractional distillation which is very troublesome in the aliphatic series. They have been used in numerous instances and can be adapted to give mixed anli3"drides. Benzoic anhydride has been obtained, by closely related procedures, from benzoic acid and benzoyl chloride by heating under reduced pressure or in the presence of zinc chloride. 

Alkanesulfinyl chlorides have been prepared by the action of thionyl chloride on alkanesulfinic acids and by the solvolysis of alkylsulfur trichlorides with water, alcohols, and organic acids. The present procedure, which appears to be general for the preparation of sulfinyl chlorides in either the aliphatic or the aromatic series, is based on an improvement in the solvolysis method whereby the use of inert solvent is eliminated and the reaction is carried out in a one-phase system. ... 

The intermediacy of dipolar species such as 186 has been demonstrated by reaction of enamines with 2-hydroxy-1-aldehydes of the aromatic series (129). The enamine (113) reacts in benzene solution at room temperature with 2-hydroxy-1-naphthaldehyde to give the crystalline adduct (188) in 91 % yield. Oxidation with chromium trioxide-pyridine of 188 gave 189 with p elimination of the morpholine moiety. Palladium on charcoal dehydrogenation of 189 gave the known 1,2-benzoxanthone (129). 

In the case of noncyclized derivatives of the aromatic series (nitrotolanes), isato-gen is obtained either by a longer heating of the substrate in pyridine, or by photochemical (sun rays) or catalytic action (69MI2) (Scheme 113). 

The interaction between a 4-iodopyrazole-3-carboxylic acid and copper ace-tylides having both donor and acceptor substituents at the triple bond generated six- rather than five-membered lactones, as in the aromatic series (Scheme 117). 

A number of the aldehydes, both of the aliphatic and aromatic series, are of the highest importance in synthetic perfumery. The relationship existing between alcohols, aldehydes, and acids is shown by the following example —... 

Aromaten, pi. aromatic substances, aromatisch, a. aromatic. — aromatisches Mittel, (Pharm.) aromatic.—aromatische Reihe, aromatic series. 

Nitric acid and especially fuming acid is a strong oxidant and nitrating agent, especially when it is combined with sulphuric acid (formation of an electrophilic species). The dangers of the reactions which involve this compound are linked to the exothermicity of the reactions and the eventual formation, particularly in an aromatic series, of nitrated species that can be very unstable in some cases. 

Finally, in an aromatic series, the effect of allyl chloride on benzene or toluene in the presence of ethyl aluminium dichloride (Friedel-Crafts catalysts) at -70 C is very violent and has led to a large number of accidents. It is thought that the exothermicity of the reaction below (in the case of benzene) caused these accidents, but one can not exclude a violent polymerisation of allyl chloride. 

Compounds consisting of only carbon and hydrogen have the simplest compositions of all organic compounds. These compounds are called hydrocarbons. It is possible to classify the hydrocarbons into four series, based on the characteristic structures of the molecules in each series. These series are known as (1) the alkane series, (2) the alkene series, (3) the alkyne series, and (4) the aromatic series. There are many subdivisions of each series, and it is also possible to have molecules that could be classified as belonging to more than one series. 

C6 H6, the simplest member of the aromatic series of hydrocarbons it is a colourless liquid with b.p. of 80 °C and is used in the manufacture of many organic compounds. 

This result, associated with those on substituent effects, supports previous conclusions to the effect that the position of the transition state depends on the reactivity in agreement with RSP. In particular, stabilization of the intermediate as a result of conjugation, such as that in the reaction of enol ethers, makes the transition state very early. The few available KSIEs also suggest that the transition states for aromatic series are earlier than those for alkenes. 

Furthermore, in the particular type of phosphate molecule under discussion (VI) we showed that when X is fluorine, compounds of high toxicity result whereas myotic effect is absent and toxicity of a low order if X = H, Et, OH, OEt, OCH2CH2C3, OCH2CH2F, Cl, NH2, NHMe, NHPh, CH2CH2F, CN, SON, etc.1 In Chapters rv and vi, however, we consider in more detail cases where X is not fluorine, but nevertheless toxicity results. Toxicity is also of a low order in the aromatic series for example, diphenyl phosphorofluoridate is relatively non-toxic and devoid of myotic properties. We also showed that ethyl phosphoro-difluoridate, (C2H50)P0F2, had neither myotic nor toxic action.1... 

Turning again to primary phosphorofluoridates (R = H), if R is substituted, e.g. in di-(2-chloroethyl) phosphorofluoridates, the toxicity and myotic effect are greatly inferior to those shown by the unsubstituted diethyl phosphorofluoridates. Toxicity is also very low in the aromatic series for example, diphenyl phos-phorofluoridate is non-toxic and devoid of myotic properties. Similar remarks apply to certain sulphur analogues, e.g. diethyl phosphorofluoridodithiolate, POF(SEt)2 (preparation, p. 54). 

The property of being converted by energetic reduction into primary amines belongs to the nitro-compounds both of the aliphatic and of the aromatic series. Six atoms of hydrogen are required for the reduction of each nitro-group. In industry nitrobenzene is reduced, not with expensive tin, but with iron filings or iron powder according to the old method of Bechamp, which is still in use at the present time. The amount of hydrochloric acid indicated by the equation... 

In the aromatic series, however, the reaction at once proceeds further. From the dithiocarbamate first formed, hydrogen sulphide is eliminated, and the phenyl isothiocyanate which remains combines, in its turn, with a second molecule of amine, giving a diarylthiourea. 

The so-called acyloin or benzoin condensation is a further interesting aldehyde reaction. In the aromatic series it takes place as a result of the action of potassium cyanide, and it is very probable that the potassium compound of the cyanohydrin is formed as an intermediate pro-... 

The reason why the acyloin synthesis is especially characteristic of aromatic aldehydes, depends on the circumstance that in the aromatic series the tertiary carbon atom in the ring does not allow of the aldol condensation, a reaction for which conditions are otherwise much more favourable. The simplest example of the acyloin condensation, moreover, was already encountered in the case of formaldehyde (p. 218) glycollic aldehyde is the simplest acyloin. Acyloin compounds are also produced, in the aliphatic series, by the action of sodium or potassium on esters, and hence are also formed as by-products in the acetoacetic ester synthesis (Bouveault, Scheibler). 

The mechanism of the coupling reaction has been very exhaustively studied. Summarising first what has already been mentioned, it must be noted that the reaction is not confined to the aromatic series, for diazo-compounds condense also with enols and with the very closely related aliphatic aci-nitro-compounds. The final products of these reactions are not azo-compounds, but the isomeric hydrazones formed from them by rearrangement. 

Hence we are justified in assuming an analogous course for the reaction in the aromatic series also (cf. Ber., 1922, 55, 2246). 

The radicle N02 also has an analogue in the aromatic series. When diphenylhydroxylamine is dehydrogenated with silver oxide the beautifully crystalline gamet-red diphenylnitrogen oxide is formed ... 

This aldehyde synthesis is applicable to compounds of the aromatic series having a labile hydrogen atom (phenyl ethers,1 naphthols,2 dialkylanilines,3-4 naphthostyril,2 anthrones 2) and to certain hydrocarbons of requisite reactivity (anthracene,5-6 7 1,2-benzanthracene,6 3,4-benzpyrene,3 7 pyrene,8 styrene,9 and a, a-diarylethylenes 9). With polynuclear hydrocarbons the best results are secured by the use of a solvent such as o-dichloro-benzene. 9-Anthraldehyde has also been prepared by the action of hydrogen cyanide and aluminum chloride on anthracene in chlorobenzene.10... 

One of these reactions, namely the oxidation of the cuprous complexes of 2-thienyl and 2- and 3-substituted thienylacetylenes, was studied in this laboratory (80). It has been found that this reaction proceeds in an analogous manner to that in other aromatic series. The yields of the corresponding diacetylenic compounds were high and depended on the oxidizing agent applied. The cuprous complexes of 2-thienylacetylene and 2- and 3-substituted thienylacetylenes are bright yellow substances, stable at room temperature. They could be readily utilized for the determination of thienylacetylenes as well as for cuprous ions. 

The observed trends in toxicities of the three characteristic aromatic series 1, 2, 3 may be explained by the factors governing n complex adsorption. It is important to realize that in toxicity studies the metal orbital factor in tt complex adsorption is held constant by confining investigations exclusively to platinum catalysts. 

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