methylene group

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Related to methylene group: methylene radical
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Noun1.methylene group - the bivalent radical CH2 derived from methane
chemical group, radical, group - (chemistry) two or more atoms bound together as a single unit and forming part of a molecule
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References in periodicals archive ?
These were assigned to the bridging methylene (I-CH2-I) and methylene group and hydrogen bonded terminal methylol functions (I-CH2-OH), respectively.
This region covers C-H stretching vibrations of phenyl ring and methylene group along with N-H as well as C=O stretching modes of amide group.
UIs formula is based on the principle that methene functional group is always next to allylic methylene group in monounsaturated fatty acids and with both allylic and diallylic methylene groups in Poly Unsaturated Fatty Acids (PUFAs).
It is simply a condensation reaction between an aldehyde or a ketone and a compound containing an active methylene group. It is promoted by various catalysts to generate chemical compounds which are used in pharmaceutical and food industries [4,5].
A wellknown catalysis mechanism includes the formation of a quinone methide intermediate and subsequent Michael type addition with the formation of a methylene group between aromatic rings [3].
While some authors believe that initial hydrogen abstraction can occur randomly, i.e., from any -CH2-group, it is more generally believed that abstraction occurs preferentially at the N-vicinal methylene group, i.e., that which is immediately adjacent to the -NH- group.
* Epoxy, urethane, aminoplast, unsaturated polyester, alkyd, silane/silicone, hybrid systems, active methylene group, etc.
Disappearance of peak after polymerization at 1650 [cm.sup.-1] which corresponds to terminal methylene group of the monomer clearly indicated the complete polymerization of vinyl group.
The determination of the methylene group distribution between chains and cycles in amorphous solids is a complicated problem and needs further research, especially the dipolar-dephasing behavior of the kerogen in the [sup.13]C NMR MAS experiment.
A preferred adhesive has a first component comprising a PRF resin mixed with a methylene group donor hardener such as paraformaldehyde.

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