Factors Affecting Reactivities

We (as well as many others (4-8), for reviews see (9,10)) have been interested for some time (11,12) in the effect of spin-state changes on reactivity. In particular, we have used computational methods to explore these effects in transition metal chemistry ((13-15), for reviews see (10,16)). The key factor affecting reactivity is the relative energy at which the zeroth-order potential energy surfaces corresponding to the individual spin-states cross (Scheme 2). This factor will determine, among other things, whether spin-forbidden reactivity is competitive with... 

The nucleophilicity of the amine is another factor affecting reactivity, and changes in it have been sometimes responsible for the observed scattering in the Brpnsted plots. The Ritchie equation80 (equation 11) has been applied to a variety of reactions in which nucleophilic addition to, or combination with, an electrophilic center is rate-limiting. 

Keough, T. DeStefano, A.J. Factors Affecting Reactivity in Ammonia CI-MS. Org. Mass Spectrom. 1981,16, 527-533. 

An inventory of factors affecting reactivity 8 Binding location and substrate positioning 9... 

We would thus predict that chlorine gas reacts with sodium metal at 298 K to give sodium chloride, and, of course, our prediction is correct. However, it is also clear that the existence of a negative AG is not the sole factor affecting reactivity. 

Strain is a very important factor affecting reactivity and this is probably best illustrated by the relative reactivities of the dienes (38), (40) and (42) [44], towards methanol giving the methoxy derivatives indicated (Scheme 22). Diene (42) reacts vigorously with neutral methanol, (40) reacts only over several days, while base is required to induce reaction with (38). 

The rates of attack of radicals on aromatic rings correlate with ionisation potential, with localisation energy and with superdelocalisability (see page 130), a picture reminiscent of the situation in aromatic electrophilic substitution. As in that field, there are evidently a number of related factors affecting reactivity. Frontier orbitals provide useful explanations for a number of observations in the field. 

It is clear from these data that ring N is a major factor affecting reactivity and orientation of attack in these systems. Nevertheless, pentafluoropyridine reacts with various nucleophiles to give products arising from exclusive attack at the 4-position (Table 9.7), whereas 37/-tetrafluoropyridine gives a mixture of both 4- and 6-attack... 

A variety of other factors affect reactivity of ethers in additions to fluorinated alkenes and we will gradually explore these. First, a process that was outlined by Muramatsu y), many years ago a 1,5—intramolecular hydrogen transfer occurs from the intermediate radical [1] and ultimately leads to a di—addition product [2]. 

From the earlier discussion on the nature of the transition state for E2 reactions, two salient factors affecting reactivity can be recognised, these being polar and steric effects. The polar effect can be divided into inductive and conjugative or electromeric components . The influence of a substituent will depend principally on the nature of the transition state, which to a large extent is determined by the leaving group and the base and solvent. A reaction... 

Revision of the factors affecting reactivity in a series of SN2-reactive molecules. 

Because E1 and Sn1 reactions proceed through the formation of a common intermediate, the two types respond in simiiar ways to factors affecting reactivities. E1 reactions are favored with substrates that can form stabie carbocations (i.e., tertiary haiides) they are also favored by the use of poor nucleophiles (weak bases) and they are generally favored by the use of polar solvents. 

Keogh, T DeStefano, A. J. (1994) Factors affecting reactivity in ammonia chemical ionization mass spectrometry. Org. Mass Spectrom. 16, 527. 

Slider motion (direct reactor reactivity control), Brayton unit speed (reactor coolant flow rate), and HRS flow all represent independent methods of affecting reactivity and are controlled by separate control systems on the spacecraft. To avoid power swings and control oscillations caused by interactions from the respective controllers, only one factor affecting reactivity may be changed at a time. Communication between the respective controllers is imperative. 

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