Molecular formula table

The vastness of organic chemistry necessitates that there be a system of organization for the naming and grouping of compounds according to their functions. This system is called the International Union of Pure and Applied Chemistry (IUPAC) system and uses prefixes that indicate the number of carbon atoms present in a molecular formula (Table 13.1). Memorizing these prefixes will be helpful to you. 

The next step in calculation of match values is the determination of fragment molecular formulas. Table 8.8 Usts all such molecular formulas where there is a peak in the spectrum corresponding to the mass of highest intensity, f(m ) > 0. The solution Xj of the optimization problem is given in the last column. We obtain a match value... 

Table 1 4 summarizes the procedure we have developed for writing Lewis structures Notice that the process depends on knowing not only the molecular formula but also the order m which the atoms are attached to one another This order of attachment is called the constitution, or connectivity, of the molecule and is determined by experiment Only rarely is it possible to deduce the constitution of a molecule from its molecular formula... 

So far we have emphasized structure in terms of electron bookkeeping We now turn our attention to molecular geometry and will see how we can begin to connect the three dimensional shape of a molecule to its Lewis formula Table 1 6 lists some simple com pounds illustrating the geometries that will be seen most often m our study of organic chemistry... 

Table 14m this section sets forth the procedure to be followed m writ mg Lewis structures for organic molecules It begins with experimentally determined information the molecular formula and the constitution (order m which the atoms are connected)... 

The compounds are arranged in the table according to their molecular formulas. Each formula is arranged alphabetically, except that C is first if carbon occurs in the molecules, followed by H if it occurs. The formulas are then arranged alphabetically and according to increasing number of atoms of each kind, all C4 compounds being listed before any C5 compounds, and so on. 

There is a more important use. Suppose a mass spectrometer has accurately measured the molecular mass of an unknown substance as 58.04189. Reference to tables of molecular mass vs. elemental composition will reveal that the molecular formula is CjH O (see Table 38.2). The molecular formula for an unknown substance can be determined which is enormously helpful in identifying it. 

Brackets signify a trivial name no longer ia use. At 101.3 kPa = 1 atm unless otherwise noted ia kPa as a subscript. At 20°C unless otherwise noted by a superscript number (°C). At 20°C unless otherwise noted. To convert to cal, divide by 4.184. 70°C. Heat of combustion (Uquid). At50°C. To convert kPa to mm Hg, multiply by 7.5. In the alkenoic series of molecular formula 2 2 metbacrylic, undecjlenic, oleic, and emcic acids have important appHcations (Table 2). Acryhc and metbacrylic acids have a petrochemical origin, and undecylenic, oleic, and emcic acids have natural origins (see Acrylic ACID AND DERIVATIVES Methacrylic acid and derivatives). Table 2. Physical Properties of the Straight-Chain Alkenoic Acids, (2n-2) 2 ... 

The molecular formula is C4H10O. Using the atomic contribution values from Table 2-386. 

The three H atoms present in the molecular formula C30//52O4 but missing from the CH balance C30//49 (Table 51.1) belong to three hydroxy groups. 

The answer to the first question is that you cannot easily calculate the number of isomers. The data in Table 2.1 were determined by a mathematician who concluded that no simple expression can calculate the number of isomers. The best way to ensure that you have written all the isomers of a par ticular- molecular- formula is to work systematically, beginning with the unbranched chain and then shortening it while adding branches one by one. It is essential that you be able to recognize when two different-looking structural formulas are actually the sane molecule written in different ways. The key point is the connectivity of the car bon chain. For example, the following group of structural... 

Lauryl alcohol is obtained from the coconut and is an ingredient in many hair shampoos. Its empirical formula is C H. A solution of 5.00 g of lauryl alcohol in 100.0 g of benzene boils at 80.78°C Using Table 10.2, find the molecular formula of lauryl alcohol... 

Arsenic and selenium, which fall directly below phosphorus and sulfur in the periodic table, are of interest for a variety of reasons. Arsenic is a true metalloid. A metallic form, called gray arsenic, has an electrical conductivity approaching that of lead. Another allotrope, yellow arsenic, is distinctly nonmetallic it has the molecular formula As4, analogous to white phosphorus, P4. Selenium is properly classified as a nonmetal, although one of its allotropes has a somewhat metallic appearance and is a semiconductor. Another form of selenium has the molecular formula Se8. analogous to sulfur. 

Carbon dioxide has the formula COj. Remembering that the prefix di means two, and tri means three, write the molecular formula for each of the following substances carbon disulfide, sulfur dioxide, sulfur trioxide. (If you don t know the symbol for an element, use the table inside the back cover of the book.)... 

The simple trend in the formulas shown by the third-row elements demonstrates the importance of the inert gas electron populations. The usefulness of the regularities is evident. Merely from the positions of two atoms in the periodic table, it is possible to predict the most likely empirical and molecular formulas. In Chapters 16 and 17 we shall see that the properties of a substance can often be predicted from its molecular formula. Thus, we shall use the periodic table continuously throughout the course as an aid in correlating and in predicting the properties of substances. 

There is little new to be said about the bonding capacity of a lithium atom. With just one valence electron, it should form gaseous molecules LiH and LiF. Because of the vacant valence orbitals, these substances will be expected only at extremely high temperatures. These expectations are in accord with the facts, as shown in Table 16-1, which summarizes the formulas and the melting and boiling points of the stable fluorides of the second-row elements. In each case, the formula given in the table is the actual molecular formula of the species found in the gas phase. 

The molecular formulas of PMs (Table 9.5) obtained by high-resolution mass spectrometry in collaboration with Prof. Y. Kishi, Harvard University, indicate that PMs are formed by the condensation of three molecules of PS and two molecules of methylamine, with the removal of four water molecules. No study has been made on their conformational isomers. 

Table 2.1 may be useful for calculating the number of carbon, bromine, chlorine, and sulfur atoms in the molecular formula. This table shows that for every 100 12C atoms there are 1.1 13C atoms. Also, for every 100 32S atoms, there are 0.8 33S atoms and 4.4 34S atoms. The following examples... 

Fluorinated compounds are frequently referred lo by code, such as F-l 15. To translate this code into a molecular formula, add 90 to 115. The firsl digit of the sum is the number of carbons the second, the number of hydrogens the third, the number ol fluorines chlorines complete the valences (i.e., C2F5CI is F-l 15 = 90 + 115 = 205. or C H Fj). A four-digit number is used for unsaturated molecules. See Tables 14.1-14.3 for the numbering system for chlorofluorocarbons. 

Suppose that 10.0 g of an organic compound used as a component of mothballs is dissolved in 80.0 g of benzene. The freezing point of the solution is 1.20°C. (a) What is an approximate molar mass of the organic compound (b) An elemental analysis of that substance indicated that the empirical formula is C3H2C1. What is its molecular formula (c) Using the atomic molar masses from the periodic table, calculate a more accurate molar mass of the compound. 

The resolution of most mass spectrometers (the ability to separate ions of similar m/z values - see Section 3.3 above) in routine use is sufficient to allow the separation of the ions containing the individual isotopes if low-molecular-weight compounds (<1000 Da) are being studied. This is illustrated in Figure 4.13 which shows the molecular-ion region of a compound having the molecular formula C35H48N8O11S determined with a mass spectrometer resolution of 1500. The masses of the isotopes present in this molecule are shown in Table 4.2. 

The most important advantages of MIP-AES as an analytical technique for GC detection of metals and metalloids are indicated in Table 7.32. MIP-AES is one of the most powerful analytical tools for selective detection in GC, and is potentially quantitative [331]. Elemental figures of merit for GC-MIP detection have been reported [332]. Microwave-induced plasmas have found much greater use in GC than in HPLC interfacing. Reviews on empirical and molecular formula determination by GC-MIP have been published [332,333]. 

Compounds are identified by an IUPAC approved name [93-ano-l], the empirical molecular formula, and the Chemical Abstracts Service Registry Number. A summary table is available for each compound which includes the reported temperature and density values, an assigned uncertainty for the density, the difference between the observed and smoothed density values and an index key to the source of the data. A complete list of references, identified by the index keys, appears at the end of the volume. 

Pharmacological studies and clinical applications of individual Gelsemium alkaloids or of the total alkaloids have never been reviewed before, so a preliminary treatment is presented in this chapter based on the limited data collected so far. For the convenience of identification, the names, molecular formulas, sources, as well as main references of all the Gelsemium alkaloids reported in the literature to date are listed in Table I. 

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