In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond.
Cis–trans isomerism, also known as geometric isomerism or configurational isomerism, is a term used in chemistry that concerns the spatial arrangement of atoms within molecules. The prefixes "cis" and "trans" are from Latin: "this side of" and "the other side of", respectively. In the context of chemistry, cis indicates that the functional groups (substituents) are on the same side of some plane, while trans conveys that they are on opposing (transverse) sides. Cis–trans isomers are stereoisomers, that is, pairs of molecules which have the same formula but whose functional groups are in different orientations in three-dimensional space. Cis-trans notation does not always correspond to E–Z isomerism, which is an absolute stereochemical description. In general, cis–trans stereoisomers contain double bonds that do not rotate, or they may contain ring structures, where the rotation of bonds is restricted or prevented. Cis and trans isomers occur both in organic molecules and in inorganic coordination complexes. Cis and trans descriptors are not used for cases of conformational isomerism where the two geometric forms easily interconvert, such as most open-chain single-bonded structures; instead, the terms "syn" and "anti" are used.
In stereochemistry, stereoisomerism, or spatial isomerism, is a form of isomerism in which molecules have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms in space. This contrasts with structural isomers, which share the same molecular formula, but the bond connections or their order differs. By definition, molecules that are stereoisomers of each other represent the same structural isomer.
Proline (symbol Pro or P) is an organic acid classed as a proteinogenic amino acid (used in the biosynthesis of proteins), although it does not contain the amino group -NH
2 but is rather a secondary amine. The secondary amine nitrogen is in the protonated form (NH2+) under biological conditions, while the carboxyl group is in the deprotonated −COO− form. The "side chain" from the α carbon connects to the nitrogen forming a pyrrolidine loop, classifying it as a aliphatic amino acid. It is non-essential in humans, meaning the body can synthesize it from the non-essential amino acid L-glutamate. It is encoded by all the codons starting with CC (CCU, CCC, CCA, and CCG).
Azobenzene is a photoswitchable chemical compound composed of two phenyl rings linked by a N=N double bond. It is the simplest example of an aryl azo compound. The term 'azobenzene' or simply 'azo' is often used to refer to a wide class of similar compounds. These azo compounds are considered as derivatives of diazene (diimide), and are sometimes referred to as 'diazenes'. The diazenes absorb light strongly and are common dyes.
In organic chemistry, an electrocyclic reaction is a type of pericyclic rearrangement where the net result is one pi bond being converted into one sigma bond or vice versa. These reactions are usually categorized by the following criteria:
In chemistry, conformational isomerism is a form of stereoisomerism in which the isomers can be interconverted just by rotations about formally single bonds. While any two arrangements of atoms in a molecule that differ by rotation about single bonds can be referred to as different conformations, conformations that correspond to local minima on the potential energy surface are specifically called conformational isomers or conformers. Conformations that correspond to local maxima on the energy surface are the transition states between the local-minimum conformational isomers. Rotations about single bonds involve overcoming a rotational energy barrier to interconvert one conformer to another. If the energy barrier is low, there is free rotation and a sample of the compound exists as a rapidly equilibrating mixture of multiple conformers; if the energy barrier is high enough then there is restricted rotation, a molecule may exist for a relatively long time period as a stable rotational isomer or rotamer. When the time scale for interconversion is long enough for isolation of individual rotamers, the isomers are termed atropisomers. The ring-flip of substituted cyclohexanes constitutes another common form of conformational isomerism.
In chemistry, octahedral molecular geometry, also called square bipyramidal, describes the shape of compounds with six atoms or groups of atoms or ligands symmetrically arranged around a central atom, defining the vertices of an octahedron. The octahedron has eight faces, hence the prefix octa. The octahedron is one of the Platonic solids, although octahedral molecules typically have an atom in their centre and no bonds between the ligand atoms. A perfect octahedron belongs to the point group Oh. Examples of octahedral compounds are sulfur hexafluoride SF6 and molybdenum hexacarbonyl Mo(CO)6. The term "octahedral" is used somewhat loosely by chemists, focusing on the geometry of the bonds to the central atom and not considering differences among the ligands themselves. For example, [Co(NH3)6]3+, which is not octahedral in the mathematical sense due to the orientation of the N−H bonds, is referred to as octahedral.
(E)-Stilbene, commonly known as trans-stilbene, is an organic compound represented by the condensed structural formula C6H5CH=CHC6H5. Classified as a diarylethene, it features a central ethylene moiety with one phenyl group substituent on each end of the carbon–carbon double bond. It has an (E) stereochemistry, meaning that the phenyl groups are located on opposite sides of the double bond, the opposite of its geometric isomer, cis-stilbene. Trans-stilbene occurs as a white crystalline solid at room temperature and is highly soluble in organic solvents. It can be converted to cis-stilbene photochemically, and further reacted to produce phenanthrene.
Ocimenes are a group of isomeric hydrocarbons. The ocimenes are monoterpenes found within a variety of plants and fruits. α-Ocimene and the two β-ocimenes differ in the position of the isolated double bond: it is terminal in the alpha isomer. α-Ocimene is cis-3,7-dimethyl-1,3,7-octatriene. β-Ocimene is trans-3,7-dimethyl-1,3,6-octatriene. β-Ocimene exists in two stereoisomeric forms, cis and trans, with respect to the central double bond. The ocimenes are often found naturally as mixtures of the various forms. The mixture, as well as the pure compounds, are oils with a pleasant odor. They are used in perfumery for their sweet herbal scent, and are believed to act as plant defense and have anti-fungal properties. Like the related acyclic terpene myrcene, ocimenes are unstable in air. Like other terpenes, the ocimenes are nearly insoluble in water, but soluble in common organic solvents.
1,2-Dichloroethene, commonly called 1,2-dichloroethylene or 1,2-DCE, is the name for a pair of organochlorine compounds with the molecular formula C2H2Cl2. They are both colorless liquids with a sweet odor. It can exist as either of two geometric isomers, cis-1,2-dichloroethene or trans-1,2-dichloroethene, but is often used as a mixture of the two. They have modest solubility in water. These compounds have some applications as a degreasing solvent. In contrast to most cis-trans compounds, the Z isomer (cis) is more stable than the E isomer (trans) by 0.4 kcal/mol.
Cycloocta-1,5-diene is a cyclic hydrocarbon with the chemical formula C8H12, specifically [−(CH2)2−CH=CH−]2.
Aconitic acid is an organic acid. The two isomers are cis-aconitic acid and trans-aconitic acid. The conjugate base of cis-aconitic acid, cis-aconitate is an intermediate in the isomerization of citrate to isocitrate in the citric acid cycle. It is acted upon by the enzyme aconitase.
Diimide, also called diazene or diimine, is a compound having the formula (NH)2. It exists as two geometric isomers, E (trans) and Z (cis). The term diazene is more common for organic derivatives of diimide. Thus, azobenzene is an example of an organic diazene.
trans-Cyclooctene is a cyclic hydrocarbon with the formula [–(CH2)6CH=CH–], where the two C–C single bonds adjacent to the double bond are on opposite sides of the latter's plane. It is a colorless liquid with a disagreeable odor.
Dichlorotetrakis(dimethyl sulfoxide) ruthenium(II) describes coordination compounds with the formula RuCl2(dmso)4, where DMSO is dimethylsulfoxide. Both cis and trans isomers are known, but the cis isomer is more common. The cis isomer is a yellow, air-stable solid that is soluble in some organic solvents. These compounds have attracted attention as possible anti-cancer drugs.
In chemistry, hyponitrite may refer to the anion N
2O2−
2 ([ON=NO]2−), or to any ionic compound that contains it. In organic chemistry, it may also refer to the group −O−N=N−O−, or any organic compound with the generic formula R1−O−N=N−O−R2, where R1 and R2 are organic groups. Such compounds can be viewed as salts and esters of respectively hyponitrous acid H
2N
2O
2 or HON=NOH.
In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers.
α-Phenylcinnamic acid is a phenylpropanoid, or, more specifically, a derivative of cinnamic acid. It has the formula C15H12O2 and appears as an off-white crystalline solid.
6-Nonenal is an organic compound with the formula C2H5CH=CH(CH2)4CHO. Other isomeric nonenal compounds are also known to exist naturally, e.g. 2-nonenal. The cis-isomer of 6-nonenal is often listed as the principal component in the aromas of muskmelon fruits. The trans-isomer is listed as an off-flavor aroma of milk foams, and thought to be a possible polypropylene odorant.
