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An electron-withdrawing group (EWG) is a group or atom that has the ability to draw electron density toward itself and away from other adjacent atoms. [1] This electron density transfer is often achieved by resonance or inductive effects.
Article 2 of the directive lists the classes of substances or preparations that are considered to be dangerous. Some, but not all, of these classes are associated with a chemical hazard symbol and/or a code. Explosives (E) Oxidizing agents (O) Flammable substances or preparations, classified as extremely flammable (F+), highly flammable (F)
The list was amended and republished in Directive 2001/59/EC. [2] The list was subsequently updated and republished in Directive 2006/102/EC. [3] The entirety of Directive 67/548/EEC, including these S-phrases, were superseded completely on 1 June 2015 by Regulation (EC) No 1272/2008 - Classification, Labelling and Packaging Regulations. [1]
The EWG removes electron density from a π system, making it less reactive in this type of reaction, [2] [3] and therefore called deactivating groups. EDGs and EWGs also determine the positions (relative to themselves) on the aromatic ring where substitution reactions are most likely to take place.
The rate of the addition reaction was accelerated by the following EDGs in increasing order: H < CH 3 < OCH 2 CH 3. When R = OCH 2 CH 3, the rate of the reaction is the fastest because the reaction has the smallest energy of activation (ΔG ‡). The ethoxy and cyano groups are able to delocalize the radical ion in the transition state, thus ...
The RoHS 2 directive (2011/65/EU) contains allowance to add new materials and 4 materials are highlighted for this attention in the original version, the amendment 2015/863 adds four additional substances to Annex II of 2011/65/EU (3/4 of the new restrictions are recommended for investigation in the original directive, ref Para 10 of preamble).
Sometimes we can use WP:PARITY sources, but ultimately if the EWG has done something important in a particular space (for positive or negative), a MEDRS source should be outlining that context for us. Sometimes other sources can work depending on specific content, but that gets tricky.
Use restrictions: Currently, only Minnesota has a use-restriction law providing that mercury sold in the state will be used only for medical, dental, instructional, research, or manufacturing purposes. Sellers must provide buyers with a material safety data sheet and have the buyer sign a statement of proper use and disposal.