Search results
Results from the WOW.Com Content Network
Initiation: The reaction is started by a free-radical source which may be a decomposing radical initiator such as AIBN. In the example in Figure 5, the initiator decomposes to form two fragments (I•) which react with a single monomer molecule to yield a propagating (i.e. growing) polymeric radical of length 1, denoted P 1 •.
This free radical generates its own active center by reaction with the monomer and eventually a new propagating chain (Pm•) is formed.3 Ultimately, chain equilibration occurs in which there is a rapid equilibrium between the actively growing radicals and the dormant compounds, thereby allowing all of the chains to grow at the same rate.
In peptide synthesis, TIPS is used as a scavenger for peptide groups being removed from the peptide sequence at the global deprotection. TIPS is able to scavenge carbocations formed in the deprotection of a peptide as it can act as a hydride donor in acidic conditions. [1] Silanes may be preferred as scavengers in place of sulfur-based scavengers.
The free radical theory of aging states that organisms age because cells accumulate free radical damage over time. [1] A free radical is any atom or molecule that has a single unpaired electron in an outer shell. [2] While a few free radicals such as melanin are not chemically reactive, most biologically relevant free radicals are highly ...
the reaction conditions can vary from bulk over solution, emulsion, miniemulsion to suspension; it is relatively inexpensive compared with competitive techniques; The steady-state concentration of the growing polymer chains is 10 −7 M by order of magnitude, and the average life time of an individual polymer radical before termination is about ...
The radical cyclization step usually involves the attack of a radical on a multiple bond. After this step occurs, the resulting cyclized radicals are quenched through the action of a radical scavenger, a fragmentation process, or an electron-transfer reaction. Five- and six-membered rings are the most common products; formation of smaller and ...
In polymer chemistry, radical polymerization (RP) is a method of polymerization by which a polymer forms by the successive addition of a radical to building blocks (repeat units). Radicals can be formed by a number of different mechanisms, usually involving separate initiator molecules.
Radiolysis from gamma rays can create strongly active free radicals in solution. This relatively simple technique uses a minimum number of chemicals. These including water, a soluble metallic salt, a radical scavenger (often a secondary alcohol), and a surfactant (organic capping agent). High gamma doses on the order of 10 4 gray are required ...