Molecular compounds nomenclature

The aim of chemical nomenclature is to be simple but unambiguous. Ionic and molecular compounds use different procedures so it is important first to identify the type of compound. To name an ionic compound, we name the ions present and then combine the names of the ions. 

Some compounds, namely molecular compounds, contain only nonmetals. Normally the compounds you need to name are binary compounds (containing only two elements). If you have highlighted the metalloids on your periodic table, everything to the right of the metalloids is a nonmetal. The following rules apply to both nonmetals and metalloids. The only nonmetal excluded from these nomenclature rules is hydrogen. 

When it is required to convey more information than is implied by a simple compositional name, other approaches to name construction are adopted. The structure of the compound under consideration generally dictates the name adopted, even though a compound may be named correctly in more ways than one. For molecular compounds, substitutive nomenclature, originally developed for naming organic compounds and the oldest systematic nomenclature still in use, is generally used. 

The nomenclature for molecular compounds is much less complicated than for ionic compounds. Molecular compounds are formed from covalently bonded nonmetallic elements. The formula for a molecule represents a stable unit of atoms, unlike a formula for an ionic compound, which only represents the simplest whole number ratio of ions. As a result, molecular formulas cannot be simplified like formulas for ionic compounds. An example would... 

Other Commissions on Nomenclature of the lUPAC have not been inactive. In biochemistry reports have been made on steroids (II), amino acids (12), vitamins (8), and carotenoids (7). A report on the nomenclature of macro-molecular compounds has been approved (6). 

Several molecular compounds have common names that you use every day, such as water, ammonia, and alcohol. But common names can cause confusion. Does ammonia mean ammonia the pure gaseous compound or a solution of ammonia in water, as it is sold in stores And, there are severed compounds known as alcohol. Clearly, a more accurate system of naming compounds is necessary. So here, and in Chapter 4, you can learn how compounds are named following the international rules of chemical nomenclature. The goal of nomenclature is to develop a name that gives all the necessary information to allow someone else to construct the formula of the compound, and vice versa. 

Chemical Nomenclature The names of simple ionic compounds, molecular compounds, and acids can all be written by examining their chemical formula. The nomenclature flowchart (Figure 5.16) shows the basic procedure for determining these names. Chemical Nomenclature Since there are so many compounds, we need a systematic way to name them. By learning these few simple rules, you will be able to name thousands of different compounds. The next time you look at the label on a consumer product, try to identify as many of the compounds as you can by examining their names. 

In this section, we discuss the nomenclature of some simple inorganic compounds. We hrst look at the naming of ionic compounds. Then, we look at the naming of some simple molecular compounds, including binary molecnlar componnds (molecular compounds of two elements) and acids. Finally, we look at hydrates of ionic compounds. These substances contain water molecules in loose association with ionic compounds. 

Chemical nomenclature is the systematic naming of compounds based on their formulas or structures. Rules are given for naming ionic compounds, binary molecular compounds, acids, and hydrates. 

The oxides of nitrogen are ideal for practicing the nomenclature of binary molecular compounds. 

Unlike ionic compounds, molecular compounds are composed of individual covalently bonded units, or molecules. Chemists use two nomenclature systems to name binary molecules. The newer system is the Stock system for naming molecular compounds, which requires an understanding of oxidation numbers. This system will be discussed in Section 2. 

Acids were first recognized as a specific class of compounds based on their properties in solutions of water. Consequently, in chemical nomenclature, the term acid usually refers to a solution in water of one of these special compounds rather than to the compound itself. For example, hydrochloric acid refers to a water solution of the molecular compound hydrogen chloride, HCl. Some common binary and oxyacids are listed in Figure 1.6. Figure 1.7 shows some common laboratory acids. 

In Section 1, we introduced the use of Roman numerals to denote ionic charges in the Stock system of naming ionic compounds. The Stock system is actually based on oxidation numbers, and it can be used as an alternative to the prefix system for naming binary molecular compounds. In the prefix system, for example, SO2 and SO3 are named sulfur dioxide and sulfur trioxide, respectively. Their names according to the Stock system are sulfur(IV) oxide and sulfur(VI) oxide. The international body that governs nomenclature has endorsed the Stock system, which is more practical for complicated compounds. Prefix-based names and Stock-system names are still used interchangeably for many simple compounds, however. 

Binaiy oxnpounds containing carbon and hydrogen are organic compounds and do rxit follow the same naming conventions as other molecular compounds. Organic compounds arxl their nomenclature ate rtscussed in detail in Chapter 10. 

The names of molecular compounds containing hydrogen do not usually conform to the systematic nomenclature guidelines. Traditionally, many of these compounds are called either by their common, nonsystematic names or by names that do not indicate explicitly the number of H atoms present ... 

The following list gives examples of the nomenclature that is used with molecular compounds. Notice that when mono and oxide are used together, one 0 is dropped. We say monoxide, not monooxide. We do the same with penta, hexa, hepta, octa, nona, and deca, dropping the a. 

The systematic lUPAC nomenclature of compounds tries to characterize compounds by a unique name. The names are quite often not as compact as the trivial names, which are short and simple to memorize. In fact, the lUPAC name can be quite long and cumbersome. This is one reason why trivial names are still heavily used today. The basic aim of the lUPAC nomenclature is to describe particular parts of the structure (fi agments) in a systematic manner, with special expressions from a vocabulary of terms. Therefore, the systematic nomenclature can be, and is, used in database systems such as the Chemical Abstracts Service (see Section 5.4) as index for chemical structures. However, this notation does not directly allow the extraction of additional information about the molecule, such as bond orders or molecular weight. 

The general formula for boric acid esters is B(OR)2. The lower molecular weight esters such as methyl, ethyl, and phenyl are most commonly referred to as methyl borate [121 -43-7] ethyl borate [130-46-9J, and phenyl borate [1095-03-0] respectively. Some of the most common boric acid esters used in industrial appHcations are Hsted in Table 1. The nomenclature in the boric acid ester series can be confusing. The lUPAC committee on boron chemistry has suggested using trialkoxy- and triaryloxyboranes (5) for compounds usually referred to as boric acid esters, trialkyl (or aryl) borates, trialkyl (or aryl) orthoborates, alkyl (or aryl) borates, alkyl (or aryl) orthoborates, and in the older Hterature as boron alkoxides and aryloxides. CycHc boric acid esters, which are trimeric derivatives of metaboric acid (HBO2), are known as boroxines (1). 

Hsynthesis from, 3, 767 Indenobenzazepines pharmacological properties, 7, 546 Indenone oxide, 2,3-diphenyl-photochromic compound, 1, 385 In deno[ 1,2-c][ 1,2,4]triazines synthesis, 3, 434 Indicated hydrogen nomenclature, 1, 33 Indigo, I, 317, 318-319, 4, 370 Baeyer synthesis, 1, 319 colour and constitution, 1, 344-345 molecular structure, 4, 162 photochromic compound, 1, 386 synthesis, 4, 247 Indigoid dyes... 

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