Substituent acyclic hydrocarbons

R H or alkyl subsituents Y = polar substituents Acyclic hydrocarbons... 

Selection of the principal chain in unsaturated branched acyclic hydrocarbons. A principal chain must be chosen upon which to base the name of branched unsaturated acyclic hydrocarbons. The general criteria listed in Table 4.10 are applied. Those that are specifically relevant to polyenes and polyynes are criterion (b), which is the maximum number of double and triple bonds considered together criterion (c), which is the maximum length criteria (d), (f) and (g) criterion (h), which is the maximum number of substituents cited as prefixes and criteria (i) and (j). 

Carbon-13 chemical shifts lend themselves conveniently to empirical analysis, because these shifts are easily measured and tend to have well-defined substituent effects. For saturated, acyclic hydrocarbons. Grant developed the formula... 

The degree of unsaturation in the molecule, i.e. the length of the conjugated polyene chromophore, has a substantial effect on retention times. Thus the acyclic hydrocarbons of the biosynthetic desaturation series, namely phytoene, phytofluene, tetrahydrolycopene, neurosporene and lycopene are well resolved, as are compounds having the same substituent group but different levels of desaturation, e.g. the 1-hydroxy-derivatives of these hydrocarbons. The 1,2-dihydrocarotenes, found in Rps. viridis are eluted later than their parent hydrocarbons e.g. 1,2-dihydroneurosporene after neurosporene. 

Several corollaries are used if chains of equal length are competing for selection as the main chain in a saturated branched acyclic hydrocarbon. The main chain is that which has the greatest number of side chains the chain whose side chains have the lowest numbered locants the chain having the greatest number of carbon atoms that have smaller side chains (methyl or ethyl rather than a complex substituent, as discussed in 6) or the chain having the least branched side chains. 

The chemical shifts of the carbons of C=C double bonds typically range from ca. 80-160 ppm a wider range of 40-210 ppm is observed with O- and N-substituents. In unsaturated acyclic hydrocarbons, they can be predicted with high accuracy (see below). To estimate the chemical shifts in all other substituted alkenes, one can use the substituent effects listed for chemical shifts in vinyl groups. However, since no configuration-dependent parameters are available, the values thus estimated are less accurate than those for unsaturated acyclic hydrocarbons. 

Branched saturated and unsaturated acyclic hydrocarbons are named as follows after the main chain has been identified the side chains are attached thereto as substituents. To define the parent chain the following order of seniority is to be observed (see also Section 6.1, p. 178) ... 

Multivalent substituent groups of acyclic hydrocarbons are designated by attaching the suffixes. ..idene and. ..idyne to the name of the corresponding monovalent group insofar as the free valences are at the same C atom. Multiple occurrence of such structural elements is taken into account with suitable multiplicative infixes. Methylene, =CH2 or -CH2-, is retained as trivial name the group =CH- is sometimes still called methine or methyne. 

There are basically two types of carotenoids those that contain one or more oxygen atoms are known as xanthophylls those that contain hydrocarbons are known as carotenes. Common oxygen substituents are the hydroxy (as in p-cryptoxanthin), keto (as in canthaxanthin), epoxy (as in violaxanthin), and aldehyde (as in p-citraurin) groups. Both types of carotenoids may be acyclic (no ring, e.g., lycopene), monocyclic (one ring, e.g., y-carotene), or dicyclic (two rings, e.g., a- and p-carotene). In nature, carotenoids exist primarily in the more stable all-trans (or all-E) forms, but small amounts of cis (or Z) isomers do occur. - ... 

Whereas the parent difluoro-vinylcyclopropane isomerizes to difluorocyclopentene under pyrolysis conditions, the corresponding alkyl compounds also lead to acyclic dienes. The activation energy for the difluoro-vinylcyclopropane isomerization is practically identical with that observed for the unsubstituted hydrocarbon [211, 212], If the alkyl group is oriented cis to the vinyl substituent, only dienes are isolated, and the process occurs at much lower, temperatures. Presumably these stereoisomers rearrange by a different mechanism (a 1,5-homodienyl hydrogen shift [213]). When the dichlorocyclopropane XVII is subjected to flash vacuum pyrolysis it isomerizes to 9,9-dichloro-bicyclo[5.3.0]dec-l(7)-ene [214],... 

Intramolecular [2 + 2] cycloaddition of acyclic substrates take place when some activating substituent is present for hydrocarbons, conjugating vinyl or phenyl groups are sufficient. Tetraene (53) gives products (54) and (55), and the diphenylheptadiene (56) is converted thermally to the bicyclo[3.2.0] system (57). ... 

A number of points regarding the chemical behavior of the streptose moiety are anomalous and will bear comment. Although a free carbonyl group seems established, streptomycin itself shows no carbonyl absorption in the ultraviolet region. Derivatives of the acyclic or aldehydo structure have hitherto exhibited such absorption. Oxidation of this aldehyde substituent to the carboxyl stage or its reduction to either the carbinol or hydrocarbon did not affect the resistance of the tertiary hydroxyl toward acetylation. However, conversion of both aldehyde functions in streptose to the carboxyl stage of oxidation made the tertiary hydroxyl easily esterifiable. ... 

The basic idea of systematic nomenclature, whose various modes of application are to be conveyed here, resides in the concept of the parent structure - an acyclic or (poly) cyclic hydrocarbon or hetero system -whose hydrogens can be substituted by other atoms, groups of atoms, or even subordinate parent systems themselves. These substituents can likewise be further substituted in various ways. At the same time there... 

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