Constitutional unit, defined

Constitutional unit having at least one site of defined stereoisomerism. 

Note The term subchain may be used to define designated subsets of the constitutional units in a chain. 

Note A chain that comprises constitutional units joined to each other through n atoms on at least one side of each constitutional unit is termed an n-strand chain, e.g., three-strand chain. If an uncertainty exists in defining n, the highest possible number is selected. 

Sequence of atoms in the constitutional unit(s) of a macromolecule, an oligomer molecule, a block, or a chain, which defines the essential topological representation. 

Whole or part of a chain comprising one or more species of constitutional unit(s) in defined sequence. 

Constitutional unit having one or more sites of defined stereoisomerism. 

Constitutional homosequence in which the relative or absolute configuration is defined at one or more sites of stereoisomerism in each constitutional unit in the main chain of a polymer molecule. 

According to the IUPAC nomenclature, oligomers1 are molecules containing a few constitutional units repetitively linked to each other. This does not define any specific molecular weight or degree of polymerization. It states, however, that the physical properties of oligomers vary with the addition or removal of one or several units. 

Many excellent reviews and books have been written concerning the photophysics of organometallic species 16-22), a detailed discussion exceeds the scope of this work. We wish to give to the reader only the photophysical basis of selected d and d complexes to follow better the discussion in the next sections. In brief, in a metal complex, its molecular constitution can be described as a metallic center surrounded by an organic coordination sphere. The electronic interplay between these units defines the character of the electronic excited states, which are the ones to undergo subsequent photophysical or photochemical processes. 

The Commission on Macromolecular Nomenclature defined 52 terms related to polymer structure, including polymer, constitutional units, monomer, polymerization, regular polymer, tactic polymer, block polymer, graft polymer, monomeric unit, degree of polymerization, addition polymerization, condensation polymerization, homopolymer. 

Define the foiiowing terms macromolecule, polymer, and plastic. When are the constitutional unit and monomeric unit of a polymer the same ... 

A polymer is defined by the International Union of Pure and Applied Chemistry (lUPAC) as a substance made of large molecules that is characterized by the multiple repetition of one or more species of atoms or group of atoms (called monomers or constitutional units) linked to each other covalently in amounts sufficient to provide a set of properties that do not vary markedly with the addition or removal of one or a few of the constitutional units. lUPAC and many other authorities... 

A polymer is defined as a substance consisting of molecules that are characterized by multiple repetitions of one or more species of atoms or groups of atoms. These repeating species of atoms or groups of atoms are designated constitutional units. A regular polymer can be described by a certain sequence of... 

Polymers of vinyl monomers having a chiral center may display optical activity, provided the stereogenic center in the side chains has predominantly a single absolute configuration. In these polymers each constitutional unit contains at least two stereogenic centers, one in the main chain and the other in the side chain. The configurational sequence distribution of the former defines the tacticity of the polymer, while the... 

It is not possible to apply (C2.1.1) down to the level of monomers and replace by the degree of polymerization N and f by the sum of the squares of the bond lengths in the monomer because the chemical constitution imposes some stiffness to the chain on the length scale of a few monomer units. This effect is accounted for by introducing the characteristic ratio defined as C- — The characteristic ratio can be detennined... 

Conjugated diene (Section 10 5) System of the type C=C—C=C in which two pairs of doubly bonded carbons are joined by a single bond The tt electrons are delocalized over the unit of four consecutive sp hybridized carbons Connectivity (Section 1 6) Order in which a molecule s atoms are connected Synonymous with constitution Constitution (Section 1 6) Order of atomic connections that defines a molecule... 

A unit is defined as a combination of elements and may or may not constitute the entire process. By definition... 

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