Parent molecule

It is well known that the electron-impact ionization mass spectrum contains both the parent and fragment ions. The observed fragmentation pattern can be usefiil in identifying the parent molecule. This ion fragmentation also occurs with mass spectrometric detection of reaction products and can cause problems with identification of the products. This problem can be exacerbated in the mass spectrometric detection of reaction products because diese internally excited molecules can have very different fragmentation patterns than themial molecules. The parent molecules associated with the various fragment ions can usually be sorted out by comparison of the angular distributions of the detected ions [8]. 

In this model, both the parent molecule and the species generated by adding or removing an electron are treated at the single-detemiinant level. 

The FIF orbitals of the parent molecule are used to describe both species. It is said that such a model neglects "orbitalrelaxation" (i.e. the reoptimization of the spin orbitals to allow them to become appropriate to the daughter species). 

Compute Projtjcl 8-3. this was Ihtt only oplion ttnlry hence, the parent molecule itself was run. 

When the parent molecules connected by the azo group are different, azo is placed between the complete names of the parent molecules, substituted or unsubstituted. Locants are placed between the affix azo and the names of the molecules to which each refers. Preference is given to the more complex parent molecule for citation as the first component, e.g., 2-aminonaphthalene-l-azo-(4 -chloro-2 -methy Ibenzene). 

The ion (M +) derived from the parent molecule by loss of an electron is called a molecular ion. Depending on the structure of substance M and the energy of the incident electron, the resulting ion (M"+) may break up (fragment) to give ions of smaller mass (A+, B, etc.). 

The use of SPPS allows synthesis of both native oligopeptides and important synthetic analogues. Many of these fragments or substituted analogues have been found to be equal to, or more potent than, the parent molecule and to exhibit long-acting and antagonistic activities. 

Antineoplastic Drugs. Cyclophosphamide (193) produces antineoplastic effects (see Chemotherapeutics, anticancer) via biochemical conversion to a highly reactive phosphoramide mustard (194) it is chiral owing to the tetrahedral phosphoms atom. The therapeutic index of the (3)-(-)-cyclophosphamide [50-18-0] (193) is twice that of the (+)-enantiomer due to increased antitumor activity the enantiomers are equally toxic (139). The effectiveness of the DNA intercalator dmgs adriamycin [57-22-7] (195) and daunomycin [20830-81-3] (196) is affected by changes in stereochemistry within the aglycon portions of these compounds. Inversion of the carbohydrate C-1 stereocenter provides compounds without activity. The carbohydrate C-4 epimer of adriamycin, epimbicin [56420-45-2] is as potent as its parent molecule, but is significandy less toxic (139). 

Oxidative Reactions. The majority of pesticides, or pesticide products, are susceptible to some form of attack by oxidative enzymes. For more persistent pesticides, oxidation is frequently the primary mode of metaboHsm, although there are important exceptions, eg, DDT. For less persistent pesticides, oxidation may play a relatively minor role, or be the first reaction ia a metaboHc pathway. Oxidation generally results ia degradation of the parent molecule. However, attack by certain oxidative enzymes (phenol oxidases) can result ia the condensation or polymerization of the parent molecules this phenomenon is referred to as oxidative coupling (16). Examples of some important oxidative reactions are ether cleavage, alkyl-hydroxylation, aryl-hydroxylation, AJ-dealkylation, and sulfoxidation. 

The metaboHsm of a material may result in the formation of a transformation product of lower intrinsic toxicity than the parent molecule ie, a process of detoxification has occurred. In other cases, the end result is a metaboHte, or metaboHtes, of intrinsically greater toxicity than the parent molecule, ie, metaboHc activation has occurred. Some examples of detoxification and metaboHc-activation processes are given in Table 2. 

It is important to appreciate that the magnitude of the absorbed dose, the relative amounts of bio transformation product, and the distribution and elimination of metaboUtes and parent compound seen with a single exposure, may be modified by repeated exposures. For example, repeated exposure may enhance mechanisms responsible for biotransformation of the absorbed material, and thus modify the relative proportions of the metaboUtes and parent molecule, and thus the retention pattern of these materials. Clearly, this could influence the likelihood for target organ toxicity. Additionally, and particularly when there is a slow excretion rate, repeated exposures may increase the possibiUty for progressive loading of tissues and body fluids, and hence the potential for cumulative toxicity. 

Although the antibacterial spectmm is similar for many of the sulfas, chemical modifications of the parent molecule have produced compounds with a variety of absorption, metaboHsm, tissue distribution, and excretion characteristics. Administration is typically oral or by injection. When absorbed, they tend to distribute widely in the body, be metabolized by the Hver, and excreted in the urine. Toxic reactions or untoward side effects have been characterized as blood dyscrasias crystal deposition in the kidneys, especially with insufficient urinary output and allergic sensitization. Selection of organisms resistant to the sulfonamides has been observed, but has not been correlated with cross-resistance to other antibiotic families (see Antibacterial AGENTS, synthetic-sulfonamides). 

Protonation or Lewis acid complexation of a heteroatom invites nucleophilic attack, including nucleophilic attack by a parent molecule. Oligomerization and polymerization are thus often the results of bringing heterocycles into an acid environment without making sure that all of the potentially nucleophilic sites are protonated. 

Applicabdity Limitations Photolysis is appropriate for difficult-to-treat chemicals (e.g., pesticides, dioxins, chlorinated organics), nitrated wastes, and those chemicals in media which permits photolyzing the waste. The waste matrix can often shield chemicals from the light (e.g., ultraviolet light absorbers, suspended solids, solid wastes). The photolysis process typically requires pretreatment to remove suspended materials, and the by-products formed may be more toxic than the parent molecules. 

When only one carbonyl or hydroxyl group is to be blocked in a multifunctional compound, the choice of the protecting group will be determined by the ease with which the group can be introduced selectively into the parent molecule. 

The geometries and relative energies of the different conformations of model chalcogen diimides E(NR)2 (E = S, Se R = H, Me, Bu and SiMe3) have been investigated by using ab initio and DET molecular orbital methods.The cis,trans conformation is predicted to be most stable with the exception of the parent molecules E(NH)2 and the unsymmetrical systems RNSNH, for which the cis,cis conformation is slightly more stable than the cis, trans isomer. 

There is some small print to the derivation the orbitals must not change during the ionization process. In other words, the orbitals for the cation produced must be the same as the orbitals for the parent molecule. Koopmans (1934) derived the result for an exact HF wavefunction in the numerical Hartree-Fock sense. It turns out that the result is also valid for wavefunctions calculated using the LCAO version of HF theory. 

The fact is that the molecular orbitals describing the resulting cation may well be quite different from those of the parent molecule. We speak of electron relaxation, and so we need to examine the problem of calculating accurate HF wavefunctions for open-shell systems. 

Adams and Slack compared the electron densities and mobile bond orders of the parent molecule (21) with those of thiazole (22) and P50 idme (23). Overlap was neglected in these simplified calculations,... 

The key intermediate, normeperidine (81), is obtained by a scheme closely akin to that used for the parent molecule, Thus, alkylation of phenylacetonitrile with the tosyl analog of the bischloroethyl amine (78) leads to the substituted piperidine... 

The breadth of the SAR in the clozapine series is demonstrated by the fact that antipsychotic activity is retained when the dibcnzdiazcpinc nucleus of the parent molecule is replaced by an imidazobenzothiadiazepine ring system which contains twice as many hetero atoms. Preparation... 

Amines with more than one functional group are named by considering the -NH2 as an amino substituent on the parent molecule. 

Amines are organic derivatives of ammonia. They are named in the IUPAC system either by adding the suffix -amine to the name of the alkyl substituent or by considering the amino group as a substituent on a more complex parent molecule. 

Molecular ion (Section 12.1) The cation produced in the mass spectrometer by loss of an electron from the parent molecule. The mass of the molecular ion corresponds to the molecular weight of the sample. 

Unfortunately the interesting consequence of a CC bond shortening upon excitation or ionization does not follow immediately. Indeed, in the ethane positive ion at least, as calculations by Pople and collaborators have shown, the ordering of the [Pg.19]

In the Chemical Abstracts method (also accepted by IUPAC Rule C-912), the naming of monoazo compounds with radicals R derived from two identical parent hydrocarbon hydrides is the same as mentioned above (for an exception see C-912.2). If the azo group links groups that are different when unsubstituted (R-N2-R ), a parent molecule RH is treated as substituted by R -N2- (Rule C-912.4) thus, 1.8 is called 4-(2-hydroxy-l-naphthylazo)benzenesulfonic acid or 4-(2-hydroxy-... 

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