Point of attachment

An alkyl group lacks one of the hydrogens of an alkane A methyl group (CH3 —) is an alkyl group derived from methane (CH4) Unbranched alkyl groups m which the point of attachment is at the end of the chain are named m lUPAC nomenclature by replac mg the ane endings of Table 2 2 by yl... 

The dash at the end of the chain represents a potential point of attachment for some other atom or group... 

Carbon atoms are classified according to their degree of substitution by other car bons A primary carbon is directly attached to one other carbon Similarly a secondary carbon is directly attached to two other carbons a tertiary carbon to three and a qua ternary carbon to four Alkyl groups are designated as primary secondary or tertiary according to the degree of substitution of the carbon at the potential point of attachment... 

Branched alkyl groups are named by using the longest continuous chain that begins at the point of attachment as the base name Thus the systematic names of the two C3H7 alkyl groups are propyl and 1 methylethyl Both are better known by their common names n propyl and isopropyl respectively... 

An isopropyl group is a secondary alkyl group Its point of attachment is to a second ary carbon atom one that is directly bonded to two other carbons... 

Those derived from isobutane are the 2 methylpropyl (isobutyl) group and the 1 1 dimethylethyl (tert butyl) group Isobutyl is a primary alkyl group because its poten tial point of attachment is to a primary carbon tert Butyl is a tertiary alkyl group because Its potential point of attachment is to a tertiary carbon... 

Consider the alkyl group having the same carbon skeleton as (CH3)4C All the hydrogens are equivalent replacing any one of them by a potential point of attachment is the same as replacing any of the others... 

Number the carbon atoms beginning at the point of attachment proceeding in the direction that follows the longest continuous chain... 

The longest continuous chain that begins at the point of attachment in the group shown contains six carbons... 

Work outward from the point of attachment com paring all the atoms attached to a particular atom before proceeding further along the chain... 

When working outward from the point of attach ment always evaluate substituent atoms one by one never as a group Because oxygen has a higher atomic number than carbon... 

Identify the substituents at the chirality center and rank them in order of decreasing precedence accord mg to the system described in Section 5 4 Precedence IS determined by atomic number working outward from the point of attachment at the chirality center... 

Potential energy diagram (Section 4 8) Plot of potential en ergy versus some arbitrary measure of the degree to which a reaction has proceeded (the reaction coordinate) The point of maximum potential energy is the transition state Primary alkyl group (Section 2 13) Structural unit of the type RCH2— in which the point of attachment is to a pnmary carbon... 

Secondary alkyl group (Section 2 13) Structural unit of the type R2CH— m which the point of attachment is to a sec ondary carbon... 

For cyclic radicals, indicated hydrogen and thereafter the point of attachment (free valency) have priority for the lowest available number. 

Positive Z values indicate a downfield shift, and an arrow indicates the point of attachment of the substituent group to the double bond. 

Another important feature is the reactivity of the phosphorodithioates with alkylating agents. When one phosphorodithioate linkage is incorporated within an oligonucleotide, it can serve as a point of attachment for reporter groups bearing an alkylating function. 

Fig. 10. The postulated interaction of a-adrenoceptor agonists with the receptor. The Easson-Stedman hypothesis suggests that (R)-noradrenaline is most potent owing to its three points of attachment () to the adrenoceptor, whereas dopamine and (5)-noradrenaline are equal in activity, but less active...

Piping supports, guides, and anchors increase local stresses on the pipe wall at the point of attachment. These stresses derive from continuously acting loads owing to the weight of the piping system carried at these points (pipe, contents, insulation), the pressure in the pipe, and any other loads such... 

Two or more cyclic units linked by single or double bonds in such a way that no new rings are formed can be named by placing the appropriate multiplying prefix (bi-, ter-, quater-, etc.) before either the name of the cyclic unit or that of the corresponding radical. Locants before the name indicate the points of attachment (examples 67 and 68). 

There still remains to be settled the point of attachment of the a-aminopropionic acid side-chain in leucenol. As the latter is unaffected by boiling hydrobromic or hydriodic acid, an ether linkage at C in 3-hydroxypyridone-4 is unlikely and as the side-chain is eliminated by either pyrolysis or the action of alkali C for the location, as suggested by Kostermanns see mimosine below) is improbable. The balance of evidence seems to be in favour of attachment to the N-atom and additional data supporting this view have been provided by Adams and Jones. ... 

The ease with which one methoxyl group is lost in this reduction was at first explained by assuming carbon atom 5 as its point of attachment, but in the following year the same authors prepared by Pschorr s method 3 4 6 7-tetramethoxyphenanthrene, colourless prisms, m.p. 124-5°, which proved to be identical with Goto s dimethylsinomenol, and on this... 

In opocinchenine the hydroxyl group must, therefore, be in the ortho-position relative to the point of attachment of the benzene ring to the quinoline nucleus. The relative positions of the two ethyl groups are determined by the fact that apocincheninic acid ethyl ether on oxidation with lead peroxide and sulphuric acid gives the lactone of hydroxyopo-cincheninic acid ethyl ether (I), which, on oxidation by sodium hypo-bromite, yields quinolylphenetoledicarboxylic acid (II). 

These substances differ structurally from niquidine (VI) by the substitution in the latter of a propylidene chain at C. Ainley and King having already found that d- and Z-dihydroquinicinols (VIII) which are y-substituted piperidine derivatives, were inactive, it appeared from these two sets of results that the strongly basic centre should not be separated by more than two carbon atoms frorn the point of attachment to the quinoline nucleus. King and Work therefore prepared a series of... 

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