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3-Methylhexane is a branched hydrocarbon with two enantiomers. [2] It is one of the isomers of heptane. The molecule is chiral, and is one of the two isomers of heptane to have this property, the other being its structural isomer 2,3-dimethylpentane. The enantiomers are (R)-3-methylhexane [3] and (S)-3-methylhexane. [4]
The bonds between various bases are well defined because of their rigid and planar shape. The spatial interactions between the two bases can be classified in 6 rigid-body parameters or intra-base pair parameters (3 translational, 3 rotational) as shown in Figure 4. [63] These parameters describe the base pairs' three dimensional conformation.
3, and the sulfite ion, SO 2− 3. In organic chemistry, molecules which have a trigonal pyramidal geometry are sometimes described as sp 3 hybridized. The AXE method for VSEPR theory states that the classification is AX 3 E 1. Phosphine, an example of a molecule with a trigonal pyramidal geometry.
An unnatural base pair (UBP) is a designed subunit (or nucleobase) of DNA which is created in a laboratory and does not occur in nature. DNA sequences have been described which use newly created nucleobases to form a third base pair, in addition to the two base pairs found in nature, A-T (adenine – thymine) and G-C (guanine – cytosine).
[3] Other molecules have a tetrahedral arrangement of electron pairs around a central atom; for example ammonia (NH 3) with the nitrogen atom surrounded by three hydrogens and one lone pair. However the usual classification considers only the bonded atoms and not the lone pair, so that ammonia is actually considered as pyramidal. The H–N–H ...
Structure of iodine heptafluoride, an example of a molecule with the pentagonal-bipyramidal coordination geometry. In chemistry, a pentagonal bipyramid is a molecular geometry with one atom at the centre with seven ligands at the corners of a pentagonal bipyramid. A perfect pentagonal bipyramid belongs to the molecular point group D 5h.
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(NH 3) 6] 3+, which is not octahedral in the mathematical sense due to the orientation of the N−H bonds, is referred to as octahedral. [2]
The degree of unwinding varies depending on the intercalator; for example, ethidium cation (the ionic form of ethidium bromide found in aqueous solution) unwinds DNA by about 26°, whereas proflavine unwinds it by about 17°. This unwinding causes the base pairs to separate, or "rise", creating an opening of about 0.34 nm (3.4 Å).