Chemical formula

A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and plus (+) and minus (−) signs. These are limited to a single typographic line of symbols, which may include subscripts and superscripts. A chemical formula is not a chemical name, and it contains no words. Although a chemical formula may imply certain simple chemical structures, it is not the same as a full chemical structural formula. Chemical formulas can fully specify the structure of only the simplest of molecules and chemical substances, and are generally more limited in power than are chemical names and structural formulas.

The simplest types of chemical formulas are called empirical formulas, which use letters and numbers indicating the numerical proportions of atoms of each type. Molecular formulas indicate the simple numbers of each type of atom in a molecule, with no information on structure. For example, the empirical formula for glucose is CH2O (twice as many hydrogen atoms as carbon and oxygen), while its molecular formula is C6H12O6 (12 hydrogen atoms, six carbon and oxygen atoms).

Sometimes a chemical formula is complicated by being written as a condensed formula (or condensed molecular formula, occasionally called a "semi-structural formula"), which conveys additional information about the particular ways in which the atoms are chemically bonded together, either in covalent bonds, ionic bonds, or various combinations of these types. This is possible if the relevant bonding is easy to show in one dimension. An example is the condensed molecular/chemical formula for ethanol, which is CH3-CH2-OH or CH3CH2OH. However, even a condensed chemical formula is necessarily limited in its ability to show complex bonding relationships between atoms, especially atoms that have bonds to four or more different substituents.

Since a chemical formula must be expressed as a single line of chemical element symbols, it often cannot be as informative as a true structural formula, which is a graphical representation of the spatial relationship between atoms in chemical compounds (see for example the figure for butane structural and chemical formulas, at right). For reasons of structural complexity, there is no condensed chemical formula (or semi-structural formula) that specifies glucose (and there exist many different molecules, for example fructose and mannose, that have the same molecular formula C6H12O6 as glucose). Linear equivalent chemical names exist that can and do specify any complex structural formula (see chemical nomenclature), but such names must use many terms (words), rather than the simple element symbols, numbers, and simple typographical symbols that define a chemical formula.

Chemical formulas may be used in chemical equations to describe chemical reactions and other chemical transformations, such as the dissolving of ionic compounds into solution. While, as noted, chemical formulas do not have the full power of structural formulas to show chemical relationships between atoms, they are sufficient to keep track of numbers of atoms and numbers of electrical charges in chemical reactions, thus balancing chemical equations so that these equations can be used in chemical problems involving conservation of atoms, and conservation of electric charge.

Al2(SO4)3
Aluminium sulfate has the chemical formula Al2(SO4)3. The form of aluminium sulfate hexadecahydrate is Al2(SO4)3·16H2O.
Structural formula for butane. Examples of other chemical formulas for butane are the empirical formula C2H5, the molecular formula C4H10 and the condensed (or semi-structural) formula CH3CH2CH2CH3.

Overview

A chemical formula identifies each constituent element by its chemical symbol and indicates the proportionate number of atoms of each element. In empirical formulas, these proportions begin with a key element and then assign numbers of atoms of the other elements in the compound, by ratios to the key element. For molecular compounds, these ratio numbers can all be expressed as whole numbers. For example, the empirical formula of ethanol may be written C2H6O because the molecules of ethanol all contain two carbon atoms, six hydrogen atoms, and one oxygen atom. Some types of ionic compounds, however, cannot be written with entirely whole-number empirical formulas. An example is boron carbide, whose formula of CBn is a variable non-whole number ratio with n ranging from over 4 to more than 6.5.

When the chemical compound of the formula consists of simple molecules, chemical formulas often employ ways to suggest the structure of the molecule. These types of formulas are variously known as molecular formulas and condensed formulas. A molecular formula enumerates the number of atoms to reflect those in the molecule, so that the molecular formula for glucose is C6H12O6 rather than the glucose empirical formula, which is CH2O. However, except for very simple substances, molecular chemical formulas lack needed structural information, and are ambiguous.

For simple molecules, a condensed (or semi-structural) formula is a type of chemical formula that may fully imply a correct structural formula. For example, ethanol may be represented by the condensed chemical formula CH3CH2OH, and dimethyl ether by the condensed formula CH3OCH3. These two molecules have the same empirical and molecular formulas (C2H6O), but may be differentiated by the condensed formulas shown, which are sufficient to represent the full structure of these simple organic compounds.

Condensed chemical formulas may also be used to represent ionic compounds that do not exist as discrete molecules, but nonetheless do contain covalently bound clusters within them. These polyatomic ions are groups of atoms that are covalently bound together and have an overall ionic charge, such as the sulfate [SO
4
]2−
ion. Each polyatomic ion in a compound is written individually in order to illustrate the separate groupings. For example, the compound dichlorine hexoxide has an empirical formula ClO
3
, and molecular formula Cl
2
O
6
, but in liquid or solid forms, this compound is more correctly shown by an ionic condensed formula [ClO
2
]+
[ClO
4
]
, which illustrates that this compound consists of [ClO
2
]+
ions and [ClO
4
]
ions. In such cases, the condensed formula only need be complex enough to show at least one of each ionic species.

Chemical formulas as described here are distinct from the far more complex chemical systematic names that are used in various systems of chemical nomenclature. For example, one systematic name for glucose is (2R,3S,4R,5R)-2,3,4,5,6-pentahydroxyhexanal. This name, interpreted by the rules behind it, fully specifies glucose's structural formula, but the name is not a chemical formula as usually understood, and uses terms and words not used in chemical formulas. Such names, unlike basic formulas, may be able to represent full structural formulas without graphs.

Empirical formula

In chemistry, the empirical formula of a chemical is a simple expression of the relative number of each type of atom or ratio of the elements in the compound. Empirical formulas are the standard for ionic compounds, such as CaCl
2
, and for macromolecules, such as SiO
2
. An empirical formula makes no reference to isomerism, structure, or absolute number of atoms. The term empirical refers to the process of elemental analysis, a technique of analytical chemistry used to determine the relative percent composition of a pure chemical substance by element.

For example, hexane has a molecular formula of C
6
H
14
, or structurally CH
3
CH
2
CH
2
CH
2
CH
2
CH
3
, implying that it has a chain structure of 6 carbon atoms, and 14 hydrogen atoms. However, the empirical formula for hexane is C
3
H
7
. Likewise the empirical formula for hydrogen peroxide, H
2
O
2
, is simply HO expressing the 1:1 ratio of component elements. Formaldehyde and acetic acid have the same empirical formula, CH
2
O
. This is the actual chemical formula for formaldehyde, but acetic acid has double the number of atoms.

Molecular formula

Molecular formulas indicate the simple numbers of each type of atom in a molecule of a molecular substance. They are the same as empirical formulas for molecules that only have one atom of a particular type, but otherwise may have larger numbers. An example of the difference is the empirical formula for glucose, which is CH2O (ratio 1:2:1), while its molecular formula is C6H12O6 (number of atoms 6:12:6). For water, both formulas are H2O. A molecular formula provides more information about a molecule than its empirical formula, but is more difficult to establish.

A molecular formula shows the number of elements in a molecule, and determines whether it is a binary compound, ternary compound, quaternary compound, or has even more elements.

Condensed formula

Isobutane numbered 2D
Isobutane structural formula
Molecular formula: C4H10
Condensed or semi-structural chemical formula: (CH3)3CH
n-Butane structural formula
Molecular formula: C4H10
Condensed or semi-structural formula: CH3CH2CH2CH3

The connectivity of a molecule often has a strong influence on its physical and chemical properties and behavior. Two molecules composed of the same numbers of the same types of atoms (i.e. a pair of isomers) might have completely different chemical and/or physical properties if the atoms are connected differently or in different positions. In such cases, a structural formula is useful, as it illustrates which atoms are bonded to which other ones. From the connectivity, it is often possible to deduce the approximate shape of the molecule.

A condensed chemical formula may represent the types and spatial arrangement of bonds in a simple chemical substance, though it does not necessarily specify isomers or complex structures. For example, ethane consists of two carbon atoms single-bonded to each other, with each carbon atom having three hydrogen atoms bonded to it. Its chemical formula can be rendered as CH3CH3. In ethylene there is a double bond between the carbon atoms (and thus each carbon only has two hydrogens), therefore the chemical formula may be written: CH2CH2, and the fact that there is a double bond between the carbons is implicit because carbon has a valence of four. However, a more explicit method is to write H2C=CH2 or less commonly H2C::CH2. The two lines (or two pairs of dots) indicate that a double bond connects the atoms on either side of them.

A triple bond may be expressed with three lines (HC≡CH) or three pairs of dots (HC:::CH), and if there may be ambiguity, a single line or pair of dots may be used to indicate a single bond.

Molecules with multiple functional groups that are the same may be expressed by enclosing the repeated group in round brackets. For example, isobutane may be written (CH3)3CH. This condensed structural formula implies a different connectivity from other molecules that can be formed using the same atoms in the same proportions (isomers). The formula (CH3)3CH implies a central carbon atom connected to one hydrogen atom and three CH3 groups. The same number of atoms of each element (10 hydrogens and 4 carbons, or C4H10) may be used to make a straight chain molecule, n-butane: CH3CH2CH2CH3.

Law of composition

In any given chemical compound, the elements always combine in the same proportion with each other. This is the law of constant composition.

The law of constant composition says that, in any particular chemical compound, all samples of that compound will be made up of the same elements in the same proportion or ratio. For example, any water molecule is always made up of two hydrogen atoms and one oxygen atom in a 2:1 ratio. If we look at the relative masses of oxygen and hydrogen in a water molecule, we see that 94% of the mass of a water molecule is accounted for by oxygen and the remaining 6% is the mass of hydrogen. This mass proportion will be the same for any water molecule.[1]

Chemical names in answer to limitations of chemical formulas

The alkene called but-2-ene has two isomers, which the chemical formula CH3CH=CHCH3 does not identify. The relative position of the two methyl groups must be indicated by additional notation denoting whether the methyl groups are on the same side of the double bond (cis or Z) or on the opposite sides from each other (trans or E). Such extra symbols violate the rules for chemical formulas, and begin to enter the territory of more complex naming systems.

As noted above, in order to represent the full structural formulas of many complex organic and inorganic compounds, chemical nomenclature may be needed which goes well beyond the available resources used above in simple condensed formulas. See IUPAC nomenclature of organic chemistry and IUPAC nomenclature of inorganic chemistry 2005 for examples. In addition, linear naming systems such as International Chemical Identifier (InChI) allow a computer to construct a structural formula, and simplified molecular-input line-entry system (SMILES) allows a more human-readable ASCII input. However, all these nomenclature systems go beyond the standards of chemical formulas, and technically are chemical naming systems, not formula systems.

Polymers in condensed formulas

For polymers in condensed chemical formulas, parentheses are placed around the repeating unit. For example, a hydrocarbon molecule that is described as CH3(CH2)50CH3, is a molecule with fifty repeating units. If the number of repeating units is unknown or variable, the letter n may be used to indicate this formula: CH3(CH2)nCH3.

Ions in condensed formulas

For ions, the charge on a particular atom may be denoted with a right-hand superscript. For example, Na+, or Cu2+. The total charge on a charged molecule or a polyatomic ion may also be shown in this way. For example: H3O+ or SO42−. Note that + and - are used in place of +1 and -1, respectively.

For more complex ions, brackets [ ] are often used to enclose the ionic formula, as in [B12H12]2−, which is found in compounds such as Cs2[B12H12]. Parentheses ( ) can be nested inside brackets to indicate a repeating unit, as in [Co(NH3)6]3+Cl3. Here, (NH3)6 indicates that the ion contains six NH3 groups bonded to cobalt, and [ ] encloses the entire formula of the ion with charge +3.

This is strictly optional; a chemical formula is valid with or without ionization information, and Hexamminecobalt(III) chloride may be written as [Co(NH3)6]3+Cl3 or [Co(NH3)6]Cl3. Brackets, like parentheses, behave in chemistry as they do in mathematics, grouping terms together – they are not specifically employed only for ionization states. In the latter case here, the parentheses indicate 6 groups all of the same shape, bonded to another group of size 1 (the cobalt atom), and then the entire bundle, as a group, is bonded to 3 chlorine atoms. In the former case, it is clearer that the bond connecting the chlorines is ionic, rather than covalent.

Isotopes

Although isotopes are more relevant to nuclear chemistry or stable isotope chemistry than to conventional chemistry, different isotopes may be indicated with a prefixed superscript in a chemical formula. For example, the phosphate ion containing radioactive phosphorus-32 is [32PO4]3−. Also a study involving stable isotope ratios might include the molecule 18O16O.

A left-hand subscript is sometimes used redundantly to indicate the atomic number. For example, 8O2 for dioxygen, and 16
8
O
2
for the most abundant isotopic species of dioxygen. This is convenient when writing equations for nuclear reactions, in order to show the balance of charge more clearly.

Trapped atoms

Endohedral fullerene
Traditional formula: MC60
The "@" notation: M@C60

The @ symbol (at sign) indicates an atom or molecule trapped inside a cage but not chemically bound to it. For example, a buckminsterfullerene (C60) with an atom (M) would simply be represented as MC60 regardless of whether M was inside the fullerene without chemical bonding or outside, bound to one of the carbon atoms. Using the @ symbol, this would be denoted M@C60 if M was inside the carbon network. A non-fullerene example is [As@Ni12As20]3−, an ion in which one As atom is trapped in a cage formed by the other 32 atoms.

This notation was proposed in 1991[2] with the discovery of fullerene cages (endohedral fullerenes), which can trap atoms such as La to form, for example, La@C60 or La@C82. The choice of the symbol has been explained by the authors as being concise, readily printed and transmitted electronically (the at sign is included in ASCII, which most modern character encoding schemes are based on), and the visual aspects suggesting the structure of an endohedral fullerene.

Non-stoichiometric chemical formulas

Chemical formulas most often use integers for each element. However, there is a class of compounds, called non-stoichiometric compounds, that cannot be represented by small integers. Such a formula might be written using decimal fractions, as in Fe0.95O, or it might include a variable part represented by a letter, as in Fe1–xO, where x is normally much less than 1.

General forms for organic compounds

A chemical formula used for a series of compounds that differ from each other by a constant unit is called a general formula. It generates a homologous series of chemical formulas. For example, alcohols may be represented by the formula CnH(2n + 1)OH (n ≥ 1), giving the homologs methanol, ethanol, propanol for n=1–3.

Hill system

The Hill system (or Hill notation) is a system of writing empirical chemical formulas, molecular chemical formulas and components of a condensed formula such that the number of carbon atoms in a molecule is indicated first, the number of hydrogen atoms next, and then the number of all other chemical elements subsequently, in alphabetical order of the chemical symbols. When the formula contains no carbon, all the elements, including hydrogen, are listed alphabetically.

By sorting formulas according to the number of atoms of each element present in the formula according to these rules, with differences in earlier elements or numbers being treated as more significant than differences in any later element or number—like sorting text strings into lexicographical order—it is possible to collate chemical formulas into what is known as Hill system order.

The Hill system was first published by Edwin A. Hill of the United States Patent and Trademark Office in 1900.[3] It is the most commonly used system in chemical databases and printed indexes to sort lists of compounds.[4]

A list of formulas in Hill system order is arranged alphabetically, as above, with single-letter elements coming before two-letter symbols when the symbols begin with the same letter (so "B" comes before "Be", which comes before "Br").[4]

The following example formulae are written using the Hill system, and listed in Hill order:

  • BrI
  • CCl4
  • CH3I
  • C2H5Br
  • H2O4S

See also

References

  1. ^ "Law of Constant Composition". Everything Math and Science. SIYAVULA. Retrieved 31 March 2016. CC-BY-SA icon.svg This material is available under a Creative Commons Attribution-Share Alike 3.0 license.
  2. ^ Chai, Yan; Guo, Ting; Jin, Changming; Haufler, Robert E.; Chibante, L. P. Felipe; Fure, Jan; Wang, Lihong; Alford, J. Michael; Smalley, Richard E. (1991). "Fullerenes wlth Metals Inside". Journal of Physical Chemistry. 95 (20): 7564–7568. doi:10.1021/j100173a002.
  3. ^ Edwin A. Hill (1900). "On a system of indexing chemical literature; Adopted by the Classification Division of the U.S. Patent Office". J. Am. Chem. Soc. 22 (8): 478–494. doi:10.1021/ja02046a005.
  4. ^ a b Wiggins, Gary. (1991). Chemical Information Sources. New York: McGraw Hill. p. 120.
  • Petrucci, Ralph H.; Harwood, William S.; Herring, F. Geoffrey (2002). "3". General chemistry: principles and modern applications (8th ed.). Upper Saddle River, N.J: Prentice Hall. ISBN 978-0-13-014329-7. LCCN 2001032331. OCLC 46872308.

External links

2-Methylphenethylamine

2-Methylphenethylamine (2MPEA) is an organic compound with the chemical formula of C9H13N. 2MPEA is a human trace amine associated receptor 1 (TAAR1) agonist, a property which it shares with its monomethylated phenethylamine isomers, such as amphetamine (α-methylphenethylamine), β-methylphenethylamine, and N-methylphenethylamine (a trace amine).Very little data, even on toxicity, is available about its effects on humans other than that it activates the human TAAR1 receptor.

3-Methylphenethylamine

3-Methylphenethylamine (3MPEA) is an organic compound with the chemical formula of C9H13N. 3MPEA is a human trace amine associated receptor 1 (TAAR1) agonist, a property which it shares with its monomethylated phenethylamine isomers, such as amphetamine (α-methylphenethylamine), β-methylphenethylamine, and N-methylphenethylamine (a trace amine).Very little data, even on toxicity, is available about its effects on humans other than that it is corrosive and activates the human TAAR1 receptor.

Aluminium(II) oxide

Aluminium(II) oxide or aluminium monoxide is a compound of aluminium and oxygen with the chemical formula AlO. It has been detected in the gas phase after explosion of aluminized grenades in the upper atmosphere and in stellar absorption spectra.

Ammonium

The ammonium cation is a positively charged polyatomic ion with the chemical formula NH+4. It is formed by the protonation of ammonia (NH3). Ammonium is also a general name for positively charged or protonated substituted amines and quaternary ammonium cations (NR+4), where one or more hydrogen atoms are replaced by organic groups (indicated by R).

Amphibole

Amphibole ( ) is an important group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain SiO4 tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Amphiboles can be green, black, colorless, white, yellow, blue, or brown. The International Mineralogical Association currently classifies amphiboles as a mineral supergroup, within which are two groups and several subgroups.

Benzothiazole

Benzothiazole is an aromatic heterocyclic compound with the chemical formula C7H5NS. It is colorless, slightly viscous liquid. Although the parent compound, benzothiazole is not widely used, many of its derivatives are found in commercial products or in nature. Firefly luciferin can be considered a derivative of benzothiazole.

Bicarbonate

In inorganic chemistry, bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. It is a polyatomic anion with the chemical formula HCO−3.

Bicarbonate serves a crucial biochemical role in the physiological pH buffering system.The term "bicarbonate" was coined in 1814 by the English chemist William Hyde Wollaston. The prefix "bi" in "bicarbonate" comes from an outdated naming system and is based on the observation that there is twice as much carbonate (CO2−3) per sodium ion in sodium bicarbonate (NaHCO3) and other bicarbonates than in sodium carbonate (Na2CO3) and other carbonates. The name lives on as a trivial name.

Casomorphin

Casomorphin is an opioid peptide (protein fragment) derived from the digestion of the milk protein casein.

Chemical compound

A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) composed of atoms from more than one element held together by chemical bonds. A chemical element bonded to an identical chemical element is not a chemical compound since only one element, not two different elements, is involved.

There are four types of compounds, depending on how the constituent atoms are held together:

molecules held together by covalent bonds

ionic compounds held together by ionic bonds

intermetallic compounds held together by metallic bonds

certain complexes held together by coordinate covalent bonds.A chemical formula is a way of expressing information about the proportions of atoms that constitute a particular chemical compound, using the standard abbreviations for the chemical elements, and subscripts to indicate the number of atoms involved. For example, water is composed of two hydrogen atoms bonded to one oxygen atom: the chemical formula is H2O. Many chemical compounds have a unique numerical identifier assigned by the Chemical Abstracts Service (CAS): its CAS number.

A compound can be converted to a different chemical composition by interaction with a second chemical compound via a chemical reaction. In this process, bonds between atoms are broken in both of the interacting compounds, and then bonds are reformed so that new associations are made between atoms.

Chromium(IV) fluoride

Chromium(IV) fluoride is an inorganic compound with the chemical formula CrF4.

Formula

In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a chemical formula. The informal use of the term formula in science refers to the general construct of a relationship between given quantities.

The plural of formula is spelt formulae (from the original Latin).

In mathematics, a formula is an entity constructed using the symbols and formation rules of a given logical language. For example, determining the volume of a sphere requires a significant amount of integral calculus or its geometrical analogue, the method of exhaustion; but, having done this once in terms of some parameter (the radius for example), mathematicians have produced a formula to describe the volume:

.

Having obtained this result, the volume of any sphere can be computed as long as its radius is known. Note that the volume V and the radius r are expressed as single letters instead of words or phrases. This convention, while less important in a relatively simple formula, means that mathematicians can more quickly manipulate larger and more complex formulas. Mathematical formulas are often algebraic, closed form, and/or analytical.

In modern chemistry, a chemical formula is a way of expressing information about the proportions of atoms that constitute a particular chemical compound, using a single line of chemical element symbols, numbers, and sometimes other symbols, such as parentheses, brackets, and plus (+) and minus (−) signs. For example, H2O is the chemical formula for water, specifying that each molecule consists of two hydrogen (H) atoms and one oxygen (O) atom. Similarly, O
3
denotes an ozone molecule consisting of three oxygen atoms and having a net negative charge.

In a general context, formulas are applied to provide a mathematical solution for real world problems. Some may be general: for example,

F = ma

This is one expression of Newton's second law, is applicable to a wide range of physical situations. Other formulas may be created to solve a particular problem: for example, using the equation of a sine curve to model the movement of the tides in a bay. In all cases, however, formulas form the basis for calculations.

Expressions are distinct from formulas in that they cannot contain an equals sign (=). When comparing formulas to grammatical sentences, expressions are more like phrases.

Hydroxymethyl

Hydroxymethyl in the field of chemistry, particularly in organic chemistry, is the name for a substituent with the structural formula -CH2-OH. The hydroxymethyl group consists of a methylene bridge (-CH2- unit) bonded to a hydroxy (-OH) group. This makes the hydroxymethyl group an alcohol. The hydroxymethyl group has the identical chemical formula with the methoxy group (-O-CH3) that differs only in the attachment site and orientation to the rest of the molecule. However, their chemical properties are different.

Molecule

A molecule is an electrically neutral group of two or more atoms held together by chemical bonds. Molecules are distinguished from ions by their lack of electrical charge. However, in quantum physics, organic chemistry, and biochemistry, the term molecule is often used less strictly, also being applied to polyatomic ions.

In the kinetic theory of gases, the term molecule is often used for any gaseous particle regardless of its composition. According to this definition, noble gas atoms are considered molecules as they are monatomic molecules.A molecule may be homonuclear, that is, it consists of atoms of one chemical element, as with oxygen (O2); or it may be heteronuclear, a chemical compound composed of more than one element, as with water (H2O). Atoms and complexes connected by non-covalent interactions, such as hydrogen bonds or ionic bonds, are typically not considered single molecules.Molecules as components of matter are common in organic substances (and therefore biochemistry). They also make up most of the oceans and atmosphere. However, the majority of familiar solid substances on Earth, including most of the minerals that make up the crust, mantle, and core of the Earth, contain many chemical bonds, but are not made of identifiable molecules. Also, no typical molecule can be defined for ionic crystals (salts) and covalent crystals (network solids), although these are often composed of repeating unit cells that extend either in a plane (such as in graphene) or three-dimensionally (such as in diamond, quartz, or sodium chloride). The theme of repeated unit-cellular-structure also holds for most condensed phases with metallic bonding, which means that solid metals are also not made of molecules. In glasses (solids that exist in a vitreous disordered state), atoms may also be held together by chemical bonds with no presence of any definable molecule, nor any of the regularity of repeating units that characterizes crystals.

N-Acetylmuramic acid

N-Acetylmuramic acid, or MurNAc, is the ether of lactic acid and N-acetylglucosamine with a chemical formula of C11H19NO8. It is part of a biopolymer in the bacterial cell wall, which is built from alternating units of N-acetylglucosamine (GlcNAc) and N-acetylmuramic acid (MurNAc), cross-linked with oligopeptides at the lactic acid residue of MurNAc. This layered structure is called peptidoglycan.

MurNAc is a monosaccharide derivative of N-acetylglucosamine.

Polyatomic ion

A polyatomic ion, also known as a molecular ion, is a charged chemical species (ion) composed of two or more atoms covalently bonded or of a metal complex that can be considered to be acting as a single unit. The prefix poly- means "many," in Greek, but even ions of two atoms are commonly referred to as polyatomic. In older literature, a polyatomic ion is also referred to as a radical, and less commonly, as a radical group. In contemporary usage, the term radical refers to free radicals that are (not necessarily charged) species with an unpaired electron.

An example of a polyatomic ion is the hydroxide ion; consisting of one oxygen atom and one hydrogen atom, hydroxide has a charge of −1. Its chemical formula is OH−. An ammonium ion is made up of one nitrogen atom and four hydrogen atoms: it has a charge of +1, and its chemical formula is NH+4.

Polyatomic ions are often useful in the context of acid-base chemistry or in the formation of salts. A polyatomic ion can often be considered as the conjugate acid/base of a neutral molecule. For example, the conjugate base of sulfuric acid (H2SO4) is the polyatomic hydrogen sulfate anion (HSO−4). The removal of another hydrogen ion yields the sulfate anion (SO2−4).

Propyl group

In organic chemistry, propyl is a three-carbon alkyl substituent with chemical formula –CH2CH2CH3 for the linear form. This substituent form is obtained by removing one hydrogen atom attached to the terminal carbon of propane. A propyl substituent is often represented in organic chemistry with the symbol Pr (not to be confused with the element praseodymium).

An isomeric form of propyl is obtained by moving the point of attachment from a terminal carbon atom to the central carbon atom, named 1-methylethyl or isopropyl. To maintain four substituents on each carbon atom, one hydrogen atom has to be moved from the middle carbon atom to the carbon atom which served as attachment point in the n-propyl variant, written as –CH(CH3)2.Linear propyl is sometimes termed normal and hence written with a prefix n- (i.e., n-propyl), as the absence of the prefix n- does not indicate which attachment point is chosen, i.e. absence of prefix does not automatically exclude the possibility of it being the branched version (i.e. i-propyl or isopropyl).In addition, there is a third, cyclic, form called cyclopropyl, or c-propyl. It is not isomeric with the other two forms, having the chemical formula -C3H5.

Structural formula

The structural formula of a chemical compound is a graphic representation of the molecular structure, showing how the atoms are arranged. The chemical bonding within the molecule is also shown, either explicitly or implicitly. Unlike chemical formulas, which have a limited number of symbols and are capable of only limited descriptive power, structural formulas provide a complete geometric representation of the molecular structure. For example, many chemical compounds exist in different isomeric forms, which have different enantiomeric structures but the same chemical formula. A structural formula is able to indicate arrangements of atoms in three-dimensional space in a way that a chemical formula may not be able to do.

Several systematic chemical naming formats, as in chemical databases, are used that are equivalent to, and as powerful as, geometric structures. These chemical nomenclature systems include SMILES, InChI and CML. These systematic chemical names can be converted to structural formulas and vice versa, but chemists nearly always describe a chemical reaction or synthesis using structural formulas rather than chemical names, because the structural formulas allow the chemist to visualize the molecules and the structural changes that occur in them during chemical reactions.

Thioescaline

Thioescaline (TE) is a pair of lesser-known psychedelic drugs with the chemical formula C12H19NO2S. They structural analogs of escaline in which an oxygen atom has been replaced with a sulfur atom. They were first synthesized by Alexander Shulgin and reported in his book PiHKAL. Very little is known about their dangers or toxicity.

Trimecaine

Trimecaine (systematic name (2,4,6-trimethylphenylcarbamoylmethyl)diethylammonium chloride, chemical formula C15H25ClN2O) is an organic compound used as a local anesthetic and cardial antiarrhythmic. It is white crystalline powder readily soluble in water and ethanol. It is an active ingredient in products available under trademarks Mesdicain, Mesocain, Mesokain and others.

Molecules
Deuterated
molecules
Unconfirmed
Related

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