|
(11) | EP 0 011 069 B1 |
| (12) | EUROPEAN PATENT SPECIFICATION |
|
|
| (54) |
Process for preparing overbased oil soluble magnesium salts Verfahren zur Herstellung öllöslicher hochbasischer Magnesiumsalze Procédé de préparation de sels de magnésium superbasiques solubles dans l'huile |
|
|
||||||||||||||||||||||||||||
| Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). |
[0001] This invention relates to over-based, oil-soluble magnesium salts of sulphonic acids having metal ratios ranging from 10 up to 40 and processes for preparing such over-based magnesium salts of sulphonic acids.
[0002] Over-based, oil-soluble magnesium salts of sulphonic acids are used as additives in oil-based compositions, such as lubricants, greases, fuels, and the like. They function as detergents and acid neutralizers, thereby reducing wear and corrosion and extending the engine life.
[0003] Highly basic magnesium salts of a sulphonic acid having a metal ratio of equivalents of magnesium to equivalents of sulphonic acid ranging from 10 up to 40 or more, particularly the higher metal ratios of 20 to 40 have been difficult to prepare in a one-step operation using MgO as a Mg source. In systems previously described, either insufficient magnesium was dispersed or an unfiltered product resulted.
[0004] It has been discovered that over-based magnesium sulphonates may be prepared in a one-step operation by using a reaction promoter system comprising (1) a carboxylic compound selected from the group of compounds consisting of lower carboxylic acids, lower carboxylic anhydrides, substituted lower carboxylic acids, metals salts and esters of lower carboxylic acids and mixture thereof, all having from 1 to 5 carbon aroms; (2) water and optionally (3) an alcohol selected from the group of compounds consisting of lower alkanols, lower alkoxy alkanols and mixtures thereof, all having from 1 to 5 carbon atoms. Such a promoter system gives a high quality over-based magnesium sulphonate having very high metal ratios which is suitable for use in various types of oil-based compositions.
[0005] It is therefore an object of the invention to provide a process for manufacturing oil-soluble, over-based magnesium salts of sulphonic acids having metal ratios ranging from 10 and upwards to 40 where the product is prepared in a one-step operation of containing the reaction mixture with an acidic gas.
[0006] It is a further object of the invention to provide a reaction promoter system for use in processes for manufacturing oil-soluble, over-based magnesium salts of sulphonic acids having metal ratios of 10 up to 40.
[0007] It is another object of the invention to provide a process for preparing a magnesium salt of a sulphonic acid having very high metal ratios wherein over-basing of the sulphonic acid is accomplished by using a promoter system in combination with a light form of magnesium oxide.
[0008] This invention provides a reaction promotor system for use in the manufacture of an over-based, oil-soluble magnesium salt of a sulphonic acid having metal ratios of from 10 up to 40, in a one-step operation of contacting an acidic gas with a mixture containing the sulphonic acid to be over-based.
[0009] According to the present invention there is provided a process for preparing an over-based oil soluble magnesium salt of a sulphonic acid having a metal ratio of equivalents of magnesium to equivalents of sulphonic acid of from 10 to 40; comprising contacting an acidic gas with a mixture comprising:
(a) an oil-soluble magnesium salt of a sulphonic acid,
(b) from 10 equivalents up to 40 equivalents of a light magnesium oxide per equivalent of sulphonic acid,
(c) a promoter system comprising:
(1) from 0.5 to 5 equivalents of an essentially oil-insoluble carboxylic compound per equivalent of sulphonic acid, said compound being selected from the group of compounds consisting of lower carboxylic acids, lower carboxylic anhydrides, substituted lower carboxylic acids, metal salts and esters of lower carboxylic acids and mixtures thereof, all having from 1 to 5 carbon atoms;
(2) from 2 to 30 equivalents of water per equivalent of sulphonic acid, and
(3) from 0 to 35 equivalents of an alcohol per equivalent of sulphonic acid, said alcohol being selected from the group consisting of lower alkanols, lower alkoxy alkanols and mixtures thereof, all having from 1 to 5 carbon atoms, and
(d) an inert solvent for lowering the viscosity of said mixture to facilitate mixing:
said contacting being conducted at a temperature ranging from 10°C (50° F) up to reflux temperature of said mixture and the volatile components being stripped from the reaction mixture after absorption of the acidic gas by the reaction mixture is at a desired level to give an over-based, oil-soluble magnesium salt of a sulphonic acid.
[0010] The reaction mixture may be filtered either before or after the stripping of the volatile components to give the product in solution or in concentrated form. 4
[0011] Additional water and/or alcohol may be added continuously or portion-wise to the reaction mixture during the time that the acidic gas is contacted with the mixture. The amount of water used in total should not exceed 30 equivalents per equivalent of sulphonic acid and the total amount of alcohol used should not exceed 35 equivalents per equivalent of sulphonic acid.
[0012] The aforementioned, and other objects, advantages and features of the invention will become apparent in the following detailed discussion of preferred embodiments according to this invention. It is understood that the following preferred embodiments are not to be interpreted as limiting the scope of the invention.
PROMOTER SYSTEM
[0013] The essentially oil-insoluble carboxylic compounds is represented by the formula:
wherein X is H, -eH20H, -CH2C" -CH2Br, -CH2COCH3, R or RNH2 and Y is H, R, or Mn where R is an alkyl radical of from 1 to 4 carbon atoms, the sum of all the carbon atoms in the R radicals not exceeding 5, and M" is an alkali or alkaline earth metal atom wherein n is an integer of 1 or 2.
[0014] Preferred oil-insoluble carboxylic compounds of this invention are acetic acid, propionic acid, butanoic acid, glycine, chloroacetic acid, bromoacetic acid, glycolic acid, ethyl acetoacetate, sodium acetate, calcium acetate, and magnesium acetate. These compounds may be used individually or in combination with one another where the amount of this promoter ranges from .5 up to 5 equivalents per equivalent of oil-soluble sulphonic acid. Preferably, the amount ranges from 0.7 to 1.3 equivalents. It has been found in most instances that if over 5 equivalents of the promoter are used, the reaction mixture becomes very viscous and although a product is obtained, the viscosity of the mixture makes the isolation of the product and the introduction of acidic gas into the mixture during the latter part of the process difficult.
[0015] The initial reaction mixture should have at least 2 equivalents of water per equivalent of sulphonic acid. The mixture may have up to 15 equivalents of water where the preferred range in the initial mixture is from 2 to 8 equivalents of water per equivalent of sulphonic acid.
[0016] Although the mechanism of the reaction is not fully understood, it is theorised that the presence of water in the reaction mixture initiates absorption of the acidic gas by the reaction mixture. There is, however, a competing reaction for the water in the formation of hydoxides of the magnesium oxide. It is therefore preferred to minimise the reaction of water with the magnesium oxide by carrying out additions of small amounts of water to the reaction mixture during the time that the acidic gas is contacted with one reaction mixture so as to ensure that water is available in the system to promote the absorption of the acidic gas. The amount of water used determines to a certain extent the value of the metal ratio in that higher amounts of water, there is usually a resultant haziness in the product. On the other hand, a deficiency of water causes higher viscosity in the reaction mixture and a lower metal ratio.
[0017] The total amount of water added to the mixture over the entire reaction time should not exceed 30 equivalents per equivalent of oil-soluble sulphonic acid used. The optimum amount of water to be used is determined by the amount of magnesium oxide used and the metal ratio desired because a larger amount of water results in a product having a higher metal ratio. Depending upon the end use of the product, it may be acceptable for the product to be hazy if used, for example, in bunker fuel oils and the like; however, higher clarity products are required in lubricating oils.
[0018] The alcohols used in this process include lower aliphatic alkanols, alkoxy alkanols, and mixtures thereof, where the number of carbon atoms does not exceed 5. Examples of the alcohols include methanol, ethanol, isopropanol, n-propanol, butanol, and pentanol. The preferred alcohol is methanol because of the low cost and ease of removal from the reaction mixture. Examples of the alkoxy alkanols include methoxy ethanol and ethoxy ethanol.
[0019] In order to initiate absorption of the acidic gas in the reaction mixture, it is not necessary to have an alcohol present in the initial mixture. It is believed, however, that the primary function of the alcohol is to promote the stability of the colloidal dispersion of magnesium salts in the oil. To this end there may be none or a small amount of alcohol in the initial reaction mixture and during contacting with the acidic gas further amounts of alcohol are added either separately or in combination with the addition of water. It has been found that lower metal ratios result if the total amount of alcohol to be added exceeds 35 equivalents per equivalent of sulphonic acid. The preferred amount to be used ranges from 4 to 20 equivalents per equivalent of sulphonic acid.
SULPHONIC ACIDS
[0020] The sulphonic acids to be used in this process are those which are widely known by those skilled in the art as oil-soluble sulphonic acids. Such compounds may be derived from natural petroleum fractions or various synthetically prepared sulphonated compounds. Typical oil-soluble sulphonic acids which may be used include:
alkane sulphonic acids, aromatic sulphonic acids, alkaryl sulphonic acids, aralkyl sulphonic acids, petroleum sulphonic acids such as mahogany sulphonic acid, petroleum sulphonic acid, paraffin wax sulphonic acid, petroleum naphthene sulphonic acid, polyalkylated sulphonic acid, and other types of sulphonic acids which may be obtained by fuming sulphuric acid treatment of petroleum fractions.
[0021] It is understood, of course, that mixtures of the sulphonic acids may be used in preparing an over-based magnesium sulphonate.
[0022] The process according to this invention is operative with low sulphonate concentrations which thereby allows the use of oil-based feed stock compositions containing as little as 10% by weight of magnesium sulphonate without further concentration of the oil-based stock.
ACIDIC GAS
[0023] As is appreciated by those skilled in the art, various types of acidic gases may be used in over-basing magnesium sulphonates. The preferred acidic gases are carbon dioxide, sulphur dioxide, nitrogen dioxide, and hydrogen sulphide. These gases are bubbled through the reaction mixture as it is being mixed to that the selected gas or gases become intimately mixed and in contact with the components of the reaction mixture.
[0024] The temperatures at which the contacting of the gas with the reaction temperature mixture according to a preferred embodiment may vary from 10 to 93.3°C (50 to 200°F), although preferably within the 48.9 to 76.7°C (120 to 170°F) range.
MAGNESIUM OXIDE
[0025] The type of magnesium oxide used in a preferred embodiment of the process is the light or active form. Such magnesium oxides are sold under the Trade Marks: MAGNESITE, available from Martin Marietta Chemicals, Hunt Valley, Maryland; MICHIGAN No. 3, MICHIGAN No. 15, MICHIGAN No. 340, available from Michigan Chemical Corporation, Chicago, Illinois; DOW L-2, DOW C-1, available from Dow Chemical Co., Midland Michigan; ELASTOMAG 170, and ELASTOMAG 20, available from Morton Chemical Co., Chicago, Illinois; MAGLITE Y, available from Whittacker, Clark and Daniels, South Plainfield, New York; LYCAL 93/711, and LYCAL 96/575 available from Pigment and Chemicals, Toronto, Canada; and MAGOX PREMIUM, available from Basic Chemical, Cleveland, Ohio. The amount of magnesium oxide used is dependent upon the metal ratio desired in the final product. The metal ratio is the ratio of the number of equivalents of magnesium in the over-based compound to the equivalents of sulphonic acid in the over-based compound. Therefore, to obtain a metal ratio of, for example, 30, there must be at least thirty equivalents of magnesium oxide per equivalent of sulphonic acid in the initial reaction mixture. It is apparent that when the reaction is carried out under less favourable conditions, at lower efficiencies, an excess of magnesium oxide beyond that determined by the metal ratio should be used to ensure sufficient incorporation of magnesium with the structure of the over-based magnesium salt of the sulphonic acid.
INERT DILUENTS
[0026] Several different types of volatile and non-volatile diluents may be used in this process. The non-volatile diluents are generally mineral or synthetic lubricating oils, such as lubricating oils having a viscosity around 0.2 St (cm2s-1) (100 SUS) at 37.8°C (100°F) or higher. The volatile diluents which are inert to the reaction are preferably hydrocarbons with boiling points ranging from 65.6 to 148.9°C (150 to 300°F). These can be aliphatic, aromatic, or a mixture of both types of solvents. For example, naphtha is a particularly useful diluent. Other types of suitable diluents include Stoddard solvent, cycloaliphatic and aromatic hydrocarbons, and corresponding halogenated hydrocarbons, such as chlorobenzene, and other conventional organic diluents generally employed in the over-basing procedures in this particular art of manufacture. The amount of diluents used is sufficient to lower the viscosity of the reaction mixture to facilitate mixing thereof during the introduction and contacting of the acidic gases with the mixture.
[0027] The length of time that the acidic gas is contacted with the reaction mixture depends upon the desired level of magnesium in the over-based magnesium sulphonate. The contacting of the gas with the mixture may be continued until no further gas is absorbed to indicate that substantially all of the magnesium oxide originally introduced into the system has been reacted to form an over-based magnesium sulphonate.
[0028] To determine when the absorption of the gas is complete, the flow rate of the gas leaving the system. When the flow rate of leaving gas almost equals the flow rate of the introduced gas, then the absorption is substantially complete.
[0029] As can be appreciated by those skilled in the art, impurities and other variations in the selected petroleum feed stocks and magnesium oxides, according to this invention, can cause the resultant product to have slightly different metal ratios than that achieved in the following examples. These examples are intended to illustrate various aspects of the invention and are not intended to limit the scope of the invention in any way.
PREPARATION 1
[0030] An oil-soluble magnesium sulphonate was prepared by charging into a 1 litre reactor, equipped with stirrer, dropping funnel, thermometer, cooling and vent, 310 gm of a solvent refined lubricating oil having a viscosity of 0.7 St (330 SUS) at 37.8°C (100°F) and while stirring vigorously, 103 gm of 25 percent by weight oleum was added dropwise over a half hour period. The temperature was maintained at 32.2 to 43.3°C (90 to 110°F). The mixture was stirred for an additional 10 minutes and then quenched with 25 gm water, 310 gm VM&P naphtha (Varnish Makers and Painters Naphtha) was added and the mixture allowed to settle in a separatory funnal for 3 hours; 80 gm spent acid was separated and removed. The organic naphtha layer was washed with 120 gm water and the aqueous lower yellowish layer was separated and discarded. To the upper sulphonic acid/naphtha layer was added 100 gm water, 10 gm methanol and 8 gm magnesium oxide. The mixture was stirred at 60°C (140°F) effecting neutralisation of the sulphonic acid and allowed to stand. The bottom aqueous layer which separated was discarded and the naphtha layer was stripped of solvent and water to give a 30 wt% solution of magnesium sulphonate in oil.
Example 1
[0031] Into a 1000 ml flask fitted with mechanical stirrer, thermometer, condenser, dropping funnel and a course cylindrical dispersion tube were charged 85 gm of the magnesium sulphonate of Preparation 1, 25 gm lubricating oil of 0.2 St (100 SUS) viscosity at 37.8°C (100°F), 140 gm naphtha and 30 gm magnesium oxide (MAGNESITE No. 569). The mixture was heated to 54.4°C (130°F) and 6 gm magnesium acetate was added. Heating was continued, and at 60°C (140°F) a mixture of water/methanol of 20 gm/16 gm respectively was added dropwise through the dropping funnel over a period of 66 minutes. At the same time carbonation was initiated at 75 ml/min and continued for 3 hours.
[0032] The product of carbonation was then filtered with the aid of diatomaceous filter aid. Water, methanol and naphtha were then stripped off by heating to 204.4°C (400°F) leaving a product which was clear and bright with a magnesium content of 9.2% which is equivalent to a metal ratio of 27.0.
Example 2
[0033] The following reagents were mixed together in a 1000 ml flask fitted with mechanical stirrer, thermometer, condenser and a course cylindrical dispersion tube:
137 g naphtha (B.P. 115.6-143.30C (240-290°F))
8 g methanol
4 g water
32 g lubricating oil
100 gm magnesium sulphonate solution made up to 45% magnesium sulphonate, 42% lubricating oil, and 13% naphtha. The sulphonic acid used to make the magnesium sulphonate is a straight chain alkyl benzene sulphonic acid of molecular weight about 500 which may be obtained from Continental Oil
30 g magnesium oxide sold under the Trade Mark MAGNESITE No. 569 available from Martin Marietta co. (USA) and
5.25 g glacial acetic acid.
[0034] The mixture was heated near its reflux temperature 65.6°C (150°F) and carbon dioxide was introduced while mixing via the dispersion tube into the mixture at a flow rate of 100 ml/min. Carbonation was continued for 2-1/2 hours, during which 8 gm water and 8 gm methanol were added after 40 minutes of carbonation and further 4 gm of water and 8 gm methanol were added after 80 minutes of carbonation.
[0035] The product of the carbonation was filtered with the aid of diatomaceous filter aid. The volatile components of solvent, water, methanol and naphtha were stripped off by heating to 204.4°C (400°F). A stream of C02 was introduced to the heated mixture to remove the last traces of solvents. The final product thus obtained was a clear and bright oil soluble solution which contained 9.4% by weight magnesium, 26.5% by weight magnesium sulphonate and had a viscosity of 1.2 St (525 SUS) at 98.9°C) (210°F). The metal ratio of the product was 14.8.
Example 3
[0036] This example illustrates the effect of temperature during carbonation. The exact procedure of Example 2 was followed except that the mixture was maintained at 32.2 to 43.3°C (90 to 110°F) during carbonation. The final product was a clear and bright oil soluble solution which contained 6.9% by weight magnesium, 26.9% by weight magnesium sulphonate. The metal ratio of the product was 10.7.
Examples 4 to 7
[0037] The results of a series of experiments are listed in Table 1 which illustrates the effect on the metal ratio in varying the amounts of methanol and water used during the carbonation step. The procedure is as for Example 2 with water/methanol addition made at 0, 40 and 80 minutes during the carbonation step.
Examples 8 to 11
[0038] Table 2 summarises results of a series of experiments which illustrate the effect of adding the water/methanol at different time intervals. The procedure used in each experiment is similar to that used in Example 2.
Examples 12 to 23
[0039] This series of experiments illustrate the effect of the amount of promoter used in terms of product quality. The results of these experiments are summarised in Table 3. The procedure for each experiment is similar to that used in Example 2.
Examples 24 to 29
[0040] Table 4 summarises the results of a series of experiments which illustrate the use of different promoters. All conditions of the procedure in each experiment are similar to that used in Example 2 except for using an equivalent amount of the different promoters as listed.
Examples 30 to 33
[0041] These examples illustrate how the sulphonic acids affect the product quality when using this process for production of magnesium containing lubricating oils. The results of the experiments are summarised in Table 5. The procedure of each experiment is similar to that used in Example 2.
Examples 34 to 46
[0042] The results of these experiments are summarised in Table 6 to illustrate the effect on the product obtained by using different commercially available magnesium oxides. The procedure in each experiment is similar to that of Example 2.
Examples 47 to 49
[0043] These experiments illustrate the use of different lower alcohols in the procedure of Example 2. The results of the experiments are summarised in Table 7.
[0044] It can be appreciated from the results of these experiments that high quality, over-based magnesium salts of sulphonic acids may be manufactured and used as additives in lubricating oils, greases and other types of oil-based products, such as fuel oils, bunker oils, etc., where the metal ratio of the additives are in the range of 5 to 40. The products are permanently soluble in many organic environments and therefore find application as additives in the field of lubricants and fuels.
(a) an oil-soluble magnesium salt of a sulphonic acid,
(b) from ten equivalents up to 40 equivalents of a light magnesium oxide per equivalent of sulphonic acid,
(c) a promoter system comprising:
(1) from 0.5 to 5 equivalents of an essentially oil-insoluble carboxylic compound per equivalent of sulphonic acid, said compound being selected from the group of compounds consisting of lower carboxylic acids, lower carboxylic anhydrides, substituted lower carboxylic acids, metal salts and esters of lower carboxylic acids and mixtures thereof, all having from 1 to 5 carbon atoms.
(2) from 2 to 30 equivalents of water per equivalent of sulphonic acid, and
(3) from 0 to 35 equivalents of an alcohol per equivalent of sulphonic acid, said alcohol being selected from the group consisting of lower alkanols, lower alkoxy alkanols and mixtures thereof, all having from 1 to 5 carbon atoms, and
(d) an inert solvent for lowering the viscosity of said mixture to facilitate mixing;
said contacting being conducted at a temperature ranging from 10°C (50°F) up to reflux temperature of said mixture and the volatile components being stripped from the reaction mixture after absorption of the acidic gas by the reaction mixture is at a desired level to give an over-based, oil-soluble magnesium salt of a sulphonic acid.
wherein X is H, -GH20H, -CH2CI, -CH2Br, -CHZCOCH3, R, or NRH2 and Y is H, R, or M" where R is an alkyl radical of from 1 to 4 carbon atoms, the sum of all the carbon atoms in the R radicals not exceeding 5 and M" is an alkali or alkaline earth metal atom wherein n is an integer of from 1 to 2.
(a) un sel de magnésium d'acide sulfonique soluble dans l'huile;
(b) de 10 à 40 équivalents d'une magnésie légère par équivalent d'acide sulfonique;
(c) un système activateur comprenant:
(1) de 0,5 à 5 équivalents d'un composé carboxylique essentiellement insoluble dans l'huile par équivalent d'acide sulfonique, ledit composé étant choisi dans le groupe des composés consistant en les acides carboxyliques inférieurs, les anhydrides carboxyliques inférieurs, les acides carboxyliques inférieurs substitués, les sels métalliques et esters d'acides carboxylique inférieurs, et leurs mélanges, tous ces composés contenant de 1 à 5 atomes de carbone;
(2) de 2 à 30 équivalents d'eau par équivalent d'acide sulfonique; et
(3) de 0 à 35 équivalents d'un alcool par équivalent d'acide sulfonique, cet alcool étant choisi dans le groupe consistant en les alcanols inférieurs, les alcoxyalcanols inférieurs et leurs mélanges, tous ces composés contenant de 1 à 5 atomes de carbone; et
(d) un solvant inerte pour abaisser la viscosité de ce mélange et faciliter le mélange;
le contact étant réalisé à une température allant de 10°C jusqu'à la température de reflux du mélange, et les composants volatils étant éliminés du mélange de réaction, lorsque le mélange de réaction a absorbé le gaz acide en quantité voulue pour former un sel de magnésium d'acide sulfonique contenant un excès de base et soluble dans l'huile.
dans laquelle X représente H, -CH20H, -CHZCI, -eH2Br, -CH2COCH3, R, ou NRH2 et Y représente H, R ou M", R représentant un radical alkyle en C1-C4, la somme de tous les atomes de carbone des radicaux R ne dépassant pas 5 et M" représentant un atome de métal alcalin ou alcalino-terreux, n étant le nombre allant de 1 à 2.
(a) ein öllösliches Magnesiumsalz einer Sulfonsäure;
(b) von 10 bis zu 40 Äquivalenten eines leichten Magnesiumoxids pro Äquivalent Sulfonsäure;
(c) ein Promotorsystem aus:
(1) von 0,5 bis 5 Äquivalenten einer im wesentlichen ölunlöslichen Karbonsäureverbindung pro Äquivalent der Sulfonsäure, wobei die Verbindung ausgewählt ist aus der Gruppe der Verbindungen, bestehend aus Niedrigkarbonsäuren, Niedrigkarbonsäureanhydriden, substituierten Niedrigkarbonsäuren, Metallsalzen und Estern von Niedrigkarbonsäuren und Mischungen davon, alle mit 1 bis 5 Kohlenstoffatomen,
(2) von 2 bis 30 Äquivalenten Wasser pro Äquivalent Sulfonsäure, und
(3) von 0 bis 35 Äquivalenten eines Alkohols pro Äquivalent Sulfonsäure, wobei der Alkohol ausgewählt ist aus der Gruppe bestehend aus aus Niedrigalkanolen, Niedrigalkoxyalkanolen und Mischungen davon, alle mit 1 bis 5 Kohlenstoffatomen; und
(d) ein inertes Lösungsmittel zur Erniedrigung der Viskosität der Mischung zum Erleichtern des Mischens;
wobei das Inberührungbringen durchgeführt wird bei einer Temperatur im Bereich von 10°C (50°F) bis zur Rückflusstemperatur der Mischung und die flüchtigen Komponenten aus dem Reaktionsgemisch nach Absorption des sauren Gases durch die Reaktionsmischung auf ein gewünschtes Niveau abgestreift werden, unter Erhalt eines überbasischen öllöslichen Magnesiumsalzes einer Sulfonsäure.
hat, worin X H, -CH2OH, -CH2C1, -CH2Br, -CHZCOCH3, R oder NRH2 und Y H, R oder M" bedeutet, wobei R ein Alkylrest mit 1 bis 4 Kohlenstoffatomen ist und die Summe aller Kohlenstoffatome in den R-Resten 5 nicht übersteigt und M" ein Alkali- oder Erdalkalimetallatom ist, worin n eine ganze Zahl von 1 bis 2 bedeutet.