Inorganic and Organic Compounds Nomenclature
Organic Compounds
Organic compounds are characterized by their composition, which typically consists of chains or rings of carbon (C) atoms linked together. Nomenclature, or the system of naming these compounds, is extensively covered in dedicated Organic Chemistry courses. Below are specific examples of various organic compounds:
2-phenylethylamine
Fluoxetine (Prozac)
N-methyl-3-phenyl-3-[4-(trifluoromethyl)phenoxy]propan-1-amine
Octyl acetate
Ascorbic acid (Vitamin C): Specifically identified by the structural representation as (5R)-[(1S)-1,2-Dihydroxyethyl]-3,4-dihydroxyfuran-2(5H)-one.
Inorganic Compounds
Inorganic compounds are defined as those that do not contain carbon-hydrogen (C-H) bonds and thus are categorized as not organic. Key characteristics include:
All inorganic compounds are overall uncharged or neutral.
Ionic compounds: These are composed of ions, which are charged species.
Hydrates of ionic compounds: These contain loosely bound water within their structure.
Molecular compounds: Composed of distinct molecules rather than ions.
Binary compounds: These contain only two different elements.
Nomenclature of Ionic Compounds
The naming conventions for ionic compounds involve both cations (positively charged ions) and anions (negatively charged ions).
Cation Naming
Cation: Typically a metal, with an important exception known as the ammonium cation (NH₄⁺).
Monoatomic cations: Are named directly after their respective chemical elements.
The charge for main group cations can be predicted based on their position within the Periodic Table.
Transition metals can form more than one monoatomic cation; the charge is indicated using Roman numerals in the name.
The old naming system distinguishes between higher and lower charges by using -ic for the higher charge and -ous for the lower charge.
Polyatomic cations are infrequent and possess unique names, as referenced in a designated Table (Table 3.4).
Anion Naming
Anion: Generally either a non-metal or a bonded group of nonmetal atoms.
Monoatomic anions are named with a root derived from the element, typically ending in -ide.
In some cases, the last letters of an element's name are altered to adopt a suffix of -ide.
Polyatomic anions are usually named after elements as well and can be referenced in Table 3.4.
Oxoanions have either -ite for those with fewer oxygen atoms or -ate for those with more oxygen atoms. In cases where there are more than two variants, prefixes hypo- (for the least oxygen) and per- (for the most oxygen) are used.
Cation and Anion Examples
Sample Ion List
Cation Name | Cation Formula | Anion Name | Anion Formula |
|---|---|---|---|
Hydrogen | H⁺ | Fluoride | F⁻ |
Lithium | Li⁺ | Chloride | Cl⁻ |
Sodium | Na⁺ | Bromide | Br⁻ |
Potassium | K⁺ | Iodide | I⁻ |
Calcium | Ca²⁺ | Oxide | O²⁻ |
Magnesium | Mg²⁺ | Sulfide | S²⁻ |
Iron (II) | Fe²⁺ | Nitrate | NO₃⁻ |
Iron (III) | Fe³⁺ | Nitrite | NO₂⁻ |
Nomenclature of Polyatomic Ions
Polyatomic ions can be structured using prefixes, roots, and suffixes to denote their compositions. A summary of these ions is outlined below:
Cations
Formula | Name | No. of O atoms |
|---|---|---|
NH₄⁺ | Ammonium | - |
H₃O⁺ | Hydronium | - |
Anions
Formula | Name | No. of O atoms |
|---|---|---|
CO₃²⁻ | Carbonate | 3 |
HCO₃⁻ | Hydrogen carbonate (bicarbonate) | 3 |
CH₃COO⁻ | Acetate | - |
CN⁻ | Cyanide | - |
Cr₂O₇²⁻ | Dichromate | 7 |
OH⁻ | Hydroxide | - |
O₂²⁻ | Peroxide | - |
Naming Hydrates
Hydrate: A compound that incorporates loosely bound water molecules. They are generally formed by the evaporation of aqueous solutions.
The loosely bound water can often be removed through processes such as heating under high temperatures or vacuum conditions, leading to an anhydrous compound.
Naming conventions for hydrates involve the following structure:
[\text{Name of anhydrous compound} + \text{prefix} + \text{hydrate}]
Examples of prefixes include hemi (for half, i.e., 1/2) and sesqui (for one and a half, i.e., 1.5).
Examples:
Calcium sulfate hemihydrate can be represented as CaSO₄ · ½ H₂O
Gypsum can be represented as CaSO₄ · 2 H₂O.
Summary of Nomenclature Systems
Inorganic Nomenclature Overview:
Ionic Compounds
The metal comes before the nonmetal, indicating its cation type and follows with the name of the anion that ends in -ide (for example, CaI₂ → calcium iodide).
Molecular Compounds
Only nonmetals are involved. Naming follows the format:
[\text{prefix} + \text{Name of 1st element} + \text{prefix} + \text{base name of 2nd element} + -ide}]Example: P₂O₅ → diphosphorus pentoxide.
Acids
Binary Acids:
Composed of hydrogen and one or more nonmetals. The naming structure involves using the word hydro followed by the anion's name, altered to end with -ic acid.
Example: HCl (aq) is named hydrochloric acid.
Oxyacids:
Oxyacids contain an oxygen atom, and the naming is derived from the associated oxoanion. If the oxoanion ends in -ate, it modifies to -ic acid. If it ends with -ite, it changes to -ous acid.
Example: H₃PO₄ corresponds to phosphoric acid based on the phosphate ion.
Examples of Nomenclature in Use
From formula to name:
CaBr₂ → calcium bromide
Ag₃N → silver nitride
CuO → copper(II) oxide
Cu(OH)₂ → copper(II) hydroxide
From name to formula:
Aluminum fluoride → AlF₃
Rubidium sulfide → Rb₂S
Plumbic iodide (lead(IV) iodide) → PbI₄
Potassium perchlorate → KClO₄
Conclusion
Mastering the nomenclature of organic and inorganic compounds is essential for the comprehension and communication of chemical information. An understanding of these naming conventions supports further study and practical application in the fields of chemistry and related disciplines.