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  • Chemical Abstracts , which began publication in 1907, is an abstracting journal published weekly by the American Chemical Society. The primary objective of this journal is to report all the new chemistry published throughout the world in periodicals, patents, government publications, dissertations, and so forth. The abstracts are brief summaries or digests of the most significant new items in those publications. It is safe to say that Chemical Abstracts is an almost indispensable means for following current advances in chemistry. The purpose of this program is to acquaint students with the nature and use of Chemical Abstracts, including its numerous indexes, so that they will be able to use this invaluable reference work efficiently.
  • Bound volumes of Chemical Abstracts can be found in most chemical libraries, as well as in the reference section of large general purpose libraries. The large number of volumes reflects the enormous growth in the total number of abstracts which have appeared in the years since 1907.
  • To obtain these abstracts, the Chemical Abstracts Service monitors nearly 12,000 periodicals published in over 100 countries in more than 50 languages. The bulk of the abstracts, however, are derived from a much smaller number of journals than this. For example, papers suitable for abstracting were found in only 8,500 journals during 1970. Of these, approximately 85 percent of the nonpatent abstracts were derived from only 2,000 journals. Some 250 “core journals,” all of whose papers are abstracted, produce about 30 percent of the papers abstracted in Chemical Abstracts.
  • Although Chemical Abstracts is published in the United States, its coverage is worldwide. About 70 percent of the abstracts are of patents and papers published in countries other than the U.S.
  • While the majority of the articles abstracted are written in English, there is an increasing number in other languages, primarily Russian, German, French, and Japanese. However, the proportion of articles published in English has increased significantly since the early 1960's, when slightly more than 43 percent of the papers abstracted were published in English and only 39 percent of the total originated in English-speaking countries. By 1970 the percentage of papers published in English had risen to 56 percent, with the proportion of papers originating in English-speaking countries remaining about the same.
  • The weekly issues of Chemical Abstracts constitute part of a volume of Chemical Abstracts. At this particular time, the January-to-June issues are defined as one volume Figure 8, for example, shows the bound issues which appeared from January to June, 1962, and which constitute Volume 56. We should point out that the bindings shown here represent those of one particular library. The color of the bindings, as well as special labels affixed to the spines of the books, will vary from library to library. July to December would constitute the next volume.
  • Although there is only a single volume number for each of the years 1960 and 1961, the Subject and the Formula Indexes had become so extensive that each was bound in two parts. Here, for example, we see the indexes for the volume published in 1967. Note that there are two sets of Subject Indexes covering the July to December issues. The Author and Formula Indexes, however, are not split in this way but cover the entire period from July to December.
  • Every abstract is classified into one of 80 subject sections. In Figure 13 we see some of the abstracts in four of these sections: Fermentations, Nonmammalian Biochemistry, Physical Organic Chemistry, and Noncondensed Aromatic Compounds.
  • The table of contents found on the first page of each weekly issue provides the names of the subject sections included in that particular issue. Any one weekly issue does not cover all 80 sections. In this particular issue, for example, the table of contents consists of 20 sections concerned with Biochemistry.
  • and 14 sections concerned with Organic Chemistry.
  • The next weekly issue covers the remaining 46 sections. In the example shown, the first 12 sections are concerned with Macromolecular Chemistry;
  • The present organization of 80 sections has existed since 1967. In previous years smaller numbers of sections were used, and each issue covered all sections. Here we see the Table of Contents page from a 1966 issue which covered 74 sections. It must be pointed out that information important to your research may appear in any of the sections. Therefore, a familiarity with, and use of, the indexes to Chemical Abstracts will help ensure that all abstracts of interest are located.
  • Also, keep in mind that the abstracts may appear anywhere from the date of publication of the article or patent to a year later, depending upon availability and acquisition difficulties. Articles from the major journals are often abstracted within a month of publication. To maintain a more current awareness than is available from consulting Chemical Abstracts, we suggest you acquaint yourself with the publications and services designed for this purpose. A discussion of these is beyond the scope of this lecture.
  • Figure 20 shows a typical abstract of a journal article, the title of which is highlighted.
  • Following the title are the names of the authors and their institutional affiliation.
  • Next comes the abbreviation of the journal name followed by the year, volume number, issue number, and page reference.
  • The language of the article is also indicated.
  • At the end of the abstract the initials or complete name of the abstractor is often included.
  • The number in the upper left-hand corner of the abstract is the abstract number, which would also be found in the indexes; it serves to identify the location of the abstract. This particular abstract is typical of the great majority of the abstracts in that it is "informative," that is, it relates to the contents of the article. In general, informative abstracts will discuss the purpose and scope of the articles, new reactions, compounds, procedures, and theories, as well as the author's interpretation of the results.
  • In 1972 the composition and printing of 17 sections of Chemical Abstracts became computerized, resulting in a slightly different appearance of the abstracts. With this computerization came the incorporation of a new kind of information not included before 1972-called the Chemical Abstracts Service Registry Numbers. These are identification numbers assigned to every compound mentioned in the abstract. We shall discuss later the purpose and use of these registry numbers. You will also note in the abstract shown that chemical names are in italics, while significant words are in capitals. The use of highlighted textual words is intended to increase the "scanability" of the text.
  • In addition to informative abstracts, Chemical Abstracts also publishes indicative abstracts, some examples of which are shown in Figure 32. Each of these abstracts contains a few sentences summarizing such literature as comprehensive reviews, publications of books, biographies, obituaries of well-known chemists, and articles on chemical education and the history of chemistry.
  • We cannot emphasize too strongly that the abstracts should only be relied upon to obtain preliminary information regarding a chemical problem. The abstract shown in Figure 34, for example, does not include many details about the synthetic procedures discussed in the article. The use of the abstract information alone, therefore, could result in a serious injury or loss of time.
  • On the other hand, an examination of the original article provides the chemist with a wealth of discussion material.
  • The experimental section of the article provides the experimental detail which would allow one to proceed with the actual synthesis of the compounds discussed.
  • Each weekly issue of the Abstracts contains an Author Index, a Numerical Patent Index, a Patent Concordance, and a Keyword Index.
  • The Author Index, an extract of which is shown here, provides a listing of all of the authors and co-authors of articles, as well as the inventors and assignees of patents, that have been abstracted.
  • To the right of the name in each column we see the numbers of the abstracts associated with the names that appear in this particular issue. The location of an abstract is straightforward. For example, to the right of the name: "Vanheertum J J," is given the number "59406T," which is the abstract number. To locate this abstract, you should look on the page on which the abstract numbers in this range appear.
  • Figure 38 shows part of the appropriate page in this issue. The approximate magnitude of the abstract numbers is provided in the upper right-hand corner of the page. The second abstract in this column reveals that Vanheertum was one of the inventors associated with a Belgian patent. The Author Index does not give the page number on which the abstract appears, except in early issues of Chemical Abstracts. We will discuss later the changes in the procedure for locating abstracts over the years.
  • Unlike the author and patent indexes, a comprehensive Subject Index to issues of Chemical Abstracts appears only at the end of each semi-annual volume. Included at the end of each weekly issue, however, is a keyword Subject Index. The index provides a quick entry to each abstract regardless of the section in which that abstract appears. The keyword entries are derived from the title, text, and/or context of the abstract.
  • Thus far we have discussed the indexes that accompany each issue. Each semi-annual volume of Chemical Abstracts concludes with separate comprehensive indexes which provide information about all abstracts and patents contained in that volume. These include not only Author and Patent Indexes and a Patent Concordance, but also Subject and Molecular Formula Indexes. More recent volumes also include an Index to Ring Systems, the Hetero-Atom-In-Context Index, the Registry of Organic Compounds, and the Index Guide. No separate comprehensive Keyword Index is published, but the Subject Index serves a similar purpose.
  • Figure 46a shows a typical page in a Subject Index. The Index includes a variety of words involving processes, types of reactions, subjects and properties of general interest, as well as chemical compounds and their derivatives.
  • Prior to 1968, the Subject Index also included italicized cross- references that indicated alternate topics or names under which the compound or subject might be located. The cross-reference feature is now found in a separate volume known as the Index Guide, which we will discuss later.
  • Figure 47 shows some Subject Index entries for a compound and its derivatives. You will note that the compound name-in this example, "ferrocenecarboxaldehyde"-is first followed by references to the compound itself, then by references to derivatives of the compound. In the case of derivatives, the compound name is not repeated, but simply represented by a dash. The first derivative is 1',2-dimethyl-ferrocenecarboxaldehyde, and reference is made to information about its nuclear magnetic resonance. The information is located in Volume 66, indicated in boldface type, in abstract number 104562p.
  • It is important to note that no reference to this particular compound is found in the abstract itself. The abstract merely states that approximately 50 isomeric derivatives of the compounds mentioned in the abstract were studied by NMR. To locate the NMR spectrum of the compound referenced in the Subject Index, one has to consult the original article.
  • You will recall that the abstract number ends with a letter, the significance of which will be described later. In addition, the abstract number is sometimes prefixed by a capitalized letter. The capital letter "P" preceding an abstract number indicates that the abstract is of a patent. When the abstract number is preceded by the letter "R," the original is a review, and when preceded by the letter "B," the original is a book.
  • Figure 50 shows an entry in a Subject Index published in 1966. The abstract number system was not used until 1967, so in this abstract the index references refer to the column number. The letter that follows the column number refers to the approximate column position at which the abstract is found. Thus, in this example, the information is found in Volume 65, in column 9851 at position "b."
  • On the page on which the abstract is located you will note that each of the two columns is headed by a column number. The index indicated that the abstract was found in column number 9851. In the central space between the two columns, the letters "a" through "h" divide the column length into eight portions. The abstract for which we are looking begins in the "b" section. This method of locating abstracts was used from 1947 to 1966.
  • Figure 52 shows the manner in which abstract locations were indexed from 1934 to 1946. In this example, the reference to paraldehyde is column 2182 The column position, however, is now indicated by the superscript number “2”. The page on which this abstract is located is shown in Figure 53.
  • Note that the abstract begins at the end of column position “2” and before column position “3”, thus accounting for the use of the superscript “2”. Superscript numbers ranged from 1 through 9. The superscript notation to designate column position was also used from 1916 to 1933, as indicated in the excerpt shown in the next figure.
  • The number "59”, however, now refers to the page on which the abstract is found.
  • As can be seen in Figure 55, the two-column format was not used during these years. In addition, the numbers corresponding to the index superscripts were not printed on the pages containing the abstracts. The position of the abstract on the page, therefore, has to be estimated from the magnitude of the superscript. In the years 1907 to 1915, entries in the Subject Index also referred to page numbers of the abstracts. No special notation, however, was used to designate page position.
  • Figure 56 shows the title page from a Formula Index. Since the molecular formula of a chemical compound is a universally accepted invariant, the Formula Index to Chemical Abstracts often provides the quickest reference to a specific compound. The Subject Index may be a less reliable index since some knowledge of nomenclature rules and indexing may be required to locate the name under which the compound is indexed. Nevertheless, the Formula Indexes should be used with caution, since your inability to find a compound may reflect either an incorrect formula assignment or a misunderstanding of the order in which the formulas would be indexed.
  • Chemical Abstracts Formula Indexes use a modified form of the Hill Indexing System. The system is essentially alphabetical except for those formulas containing carbon and hydrogen. In the latter case, carbon comes first, followed by hydrogen. Then the other elements follow alphabetically.
  • The ordering of elements within a formula is relatively straightforward. For example, in the top compound aluminum is placed first followed by calcium and oxygen. The second compound, C 2 H 5 AlBr 2 , contains carbon and is therefore indexed under that element. Note that, as we mentioned, hydrogen is placed after carbon with the other elements following in alphabetical order.
  • The relative sequence of formulas of carbon-containing compounds is also strictly alphabetical. However, because carbon and hydrogen appear first in such formulas special care must be taken in searching for carbon compounds. Note, for example, that in the formula CHCl 3 , chlorine follows hydrogen in accordance with the Hill system. However, the compound CCl 4 is indexed before CH and CHCl 3 because Cl appears before H in the alphabetical sequence.
  • Several entries from a Formula Index are shown in Figure 59. Beneath each formula are found the names of the compounds as given in the Subject Index. In this example, under the formula C 2 H 2 N are found references to two different compounds having this formula
  • Several entries from a Formula Index are shown in Figure 59. Beneath each formula are found the names of the compounds as given in the Subject Index. In this example, under the formula C 2 H 2 N are found references to two different compounds having this formula
  • Let us next consider the case of organic acids. The salts of simple organic acids, such as carbonic, formic, acetic, and oxalic, are found under the formula of the salts. For example, in Figure 62 we see that the rhodium, tin, zinc, and uranyl salts of formic acid are indexed in this manner.
  • The Registry Number Index is a new index which was first published with Volume 71 in 1969. All compounds are assigned an identifying or registry number by the Chemical Abstracts Service. A registry number bears no relationship to the composition or to the molecular structure of a chemical substance. Rather, the numbers are assigned in sequential order as substances are entered for the first time into the Chemical Registry System. Many original papers now include the registry numbers of all compounds discussed.
  • Let us illustrate the use of the Registry Number index. Figure 71 shows an excerpt of an article from the Journal of Organic Chemistry in which the reactions of a-difluoramino-fluorimines are discussed. Suppose you were interested in locating the name of the compound indicated by the author as number 53.
  • At the end of the article is provided a list of the registry numbers of all the compounds. Compound 53 is given a registry number of 20116-43-2. To determine the name of the compound, you would then consult the Registry Number Index under this number.
  • Below the registry number is given the name of the compound and its molecular formula. If you were interested in locating the Chemical Abstracts reference to this article, you would consult the Subject Index under the name.
  • The Subject Index entries for names of compounds now contain an additional piece of information, namely the registry number, contained in brackets. For the compound in question a reference will be found in abstract number 70208p.
  • The Registry Number Index can serve another purpose. The registry number that accompanies the name of a compound in the Subject Index can be used to obtain the molecular formula of the compound.
  • The molecular formula is provided under the registry number of the compound.
  • The registry numbers are not only found associated with compounds indexed in the Subject Index, but are also found in the Formula Index following the name of each substance having a particular formula
  • For example, the compound shown in Figure 95 is a bifunctional compound and could be named as a derivative of benzene, aniline, or phenol. Two reasonable names are shown in the figure. In a journal article, the author's choice of a name is often based on a consideration of an entire series of compounds in his papers, and not on a single member of the series. The name that he uses may or may not correspond to the name used by Chemical Abstracts in indexing it. If the structure or formula is known, a good approach to locating references for a compound such as this one is to use the Formula Index.
  • The correctly indexed name is provided under the formula with a number of abstract references. You will note that no reference is made to an aniline derivative. Also, you should check the Subject Index under the correct name to locate additional references that might not be included in the Formula Index. Generally, however, the references are identical in both indexes.
  • If, on the other hand, you were given only the name of the compound, as for example "para-hydroxyaniline," you would consult the Subject Index under the name "Aniline." Under the index entries to a long series of aniline derivatives you would find a reference to "aryl-hydroxyaniline" with the note "see Phenol, amino." This indicates that such aniline compounds are indexed as derivatives of phenol.
  • Figure 98 shows some of the Subject Index entries for phenol derivatives. Under "para-aminophenol" are found a large number of abstract references. It is important to note that the number of abstract references found in the Subject Index, not all of which are shown in this figure, greatly exceeds those found in the Formula Index. However, all of the Formula Index references are included in the Subject Index. The correct name in this example was located because the Subject Index provided a cross-reference from a common name to the indexed name. If you examine a Subject Index that has appeared since 1968, however, you will find no reference at all to hydroxyaniline compounds.
  • Figure 100 shows how the indexed name is located in the Index Guide. Again, you will note that under "aryl-hydroxyaniline" compounds, you are referred to "aminophenols." The Index Guide provides no references at all under the correctly indexed name. Therefore, having determined the correct name for the compound, you must then use the Subject Index.
  • In the section concerning the indexing priority of poly-functional compounds, a tabular summary indicates that the amine function has a lower priority than phenol. The bi-functional compound we have been discussing should therefore be indexed as a derivative of phenol. A study of this general discussion of the Subject Index is recommended, since it contains further useful information to the chemist.
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