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Prefixes geometrical

The Diels-Alder reaction of a diene with a substituted olefinic dienophile, e.g. 2, 4, 8, or 12, can go through two geometrically different transition states. With a diene that bears a substituent as a stereochemical marker (any substituent other than hydrogen deuterium will suffice ) at C-1 (e.g. 11a) or substituents at C-1 and C-4 (e.g. 5, 6, 7), the two different transition states lead to diastereomeric products, which differ in the relative configuration at the stereogenic centers connected by the newly formed cr-bonds. The respective transition state as well as the resulting product is termed with the prefix endo or exo. For example, when cyclopentadiene 5 is treated with acrylic acid 15, the cw fo-product 16 and the exo-product 17 can be formed. Formation of the cw fo-product 16 is kinetically favored by secondary orbital interactions (endo rule or Alder rule) Under kinetically controlled conditions it is the major product, and the thermodynamically more stable cxo-product 17 is formed in minor amounts only. [Pg.91]

If several groups are attached to the benzene ring, their names as well as their relative positions should be indicated. For example, dimethylbenzene or xylene, CgH (CH,)2, has three geometric isomers, with prefixes ortho-, meta-, and para-, indicating the relative positions of the two methyl groups. [Pg.311]

One of the most commonly used measures of central tendency is the mean, more correctly (but rarely) called the arithmetic mean, a term that unambiguously distinguishes it from the geometric mean. While very informative in some circumstances, the geometric mean is less commonly used, and, in the absence of the prefix arithmetic or geometric, the default interpretation of the term mean is the arithmetic mean. This is the convention followed in the rest of this book. The mean of a set of data points is therefore defined as their sum divided by the total number of data points. [Pg.86]

Prefixes (/)- and (E)- identify geometrical isomers that differ in the relative orientation of groups on either side of a double bond in a side chain. The IUPAC rules [93-ano-l] apply, thus (Zf-(l-methyl-2-propenyl)benzene is ... [Pg.12]

For compounds that show geometric isomerism, add the appropriate prefix cis- or trans-, or E- or Z-. Cycloalkenes are assumed to be cis unless named otherwise. [Pg.293]

The prefixes cis- and trans- designate adjacent and opposite geometric locations. Examples are in Figures 9-1 and 9-5. Other prefixes are used as well and will be introduced as needed in the text. [Pg.308]

This method is useful for portraying chemical formulae in typescripts and manuscripts, as a lot of information is conveyed in a condensed manner. However, it suffers from the problem that it does not give a pictorial representation of the stereochemistry of the molecule. In order to overcome this deficiency, it is possible to include the appropriate Cahn-Ingold-Prelog prefix, namely R or S, to indicate diastereo details, or one of the cis, trans, ortho, meta or para prefixes to indicate geometrical details. ... [Pg.408]

Geometrical isomers of organic compounds are distinguished by the italicized prefixes cis (from the Latin word for on this side) and trans (from the Latin word for across). [Pg.234]

Because the linear arrangement about the triple bond does not lead to geometric isomerism, the prefixes cis- and tram- are not used. [Pg.1059]

Latin, meaning across ) indicating that one of two geometrical isomers in which certain atoms or groups are on opposite sides of a plane upper explosive (flammable) limit in air, % by volume at room temperature or other temperature as noted prefix for asymmetric symbol for greater than symbol for less than symbol for less than or equal to symbol for greater than or equal to percent... [Pg.1295]


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See also in sourсe #XX -- [ Pg.34 ]




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