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Another example of this is the relationship between oleic acid and elaidic acid; oleic acid, the cis isomer, has a melting point of 13.4 °C, making it a liquid at room temperature, while the trans isomer, elaidic acid, has the much higher melting point of 43 °C, due to the straighter trans isomer being able to pack more tightly, and is solid ...
Elaidic acid has 18 carbons and is a trans-9-mono-unsaturated fatty acid. It is also a trans isomer of oleic acid. C 17 H 33 CO 2 H, IUPAC organization name (E)-octadec-9-enoic acid, numerical representation 18:1 (9), n-9, molecular weight 282.46, melting point 43–45 °C. CAS Registry Number 112-79-8.
See: cis–trans isomerism. cis (left) and trans (right) configured double bond in maleic acid and fumaric acid. cis (left) and trans (right) isomerism in a ring system. The descriptors cis (lat. on this side of) [2] and trans (lat. over, beyond) [3] are used in various contexts for the description of chemical configurations: [4] [5]
Traditionally, double bond stereochemistry was described as either cis (Latin, on this side) or trans (Latin, across), in reference to the relative position of substituents on either side of a double bond. A simple example of cis–trans isomerism is the 1,2-disubstituted ethenes, like the dichloroethene (C 2 H 2 Cl 2) isomers shown below. [7]
For ML a 4 L b 2, two isomers exist.These isomers of ML a 4 L b 2 are cis, if the L b ligands are mutually adjacent, and trans, if the L b groups are situated 180° to each other. It was the analysis of such complexes that led Alfred Werner to the 1913 Nobel Prize–winning postulation of octahedral complexes.
The methyl groups off carbons 1 and 3 are trans with respect to each other, while the methyl group off carbon 2 has undefined stereochemistry, allowing it to be either cis or trans with respect to methyl 1 or 3. [2] Each carbon atom within the cyclopentane ring is sp 3 hybridized with the theoretical C-C-C bond angles near 108 degrees.
In chemistry, isomers are molecules or polyatomic ions with identical molecular formula – that is, the same number of atoms of each element – but distinct arrangements of atoms in space. [1] Isomerism refers to the existence or possibility of isomers.
The trans form is preferred overwhelmingly in most peptide bonds (roughly 1000:1 ratio in trans:cis populations). However, X-Pro peptide groups tend to have a roughly 30:1 ratio, presumably because the symmetry between the C α and C δ atoms of proline makes the cis and trans isomers nearly equal in energy, as shown in the figure below.