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The +M effect, also known as the positive mesomeric effect, occurs when the substituent is an electron donating group. The group must have one of two things: a lone pair of electrons, or a negative charge. In the +M effect, the pi electrons are transferred from the group towards the conjugate system, increasing the density of the system.
Prior to Typhoon Yagi forming and making landfall in Vietnam, domestic media reported unusual weather patterns in August 2024. Speaking to the Natural Resources and Environment newspaper, Mai Văn Khiêm, Director of the National Center for Hydro-Meteorological Forecasting, stated that the country's average temperature reached 28.3 °C (82.9 °F), the highest in recorded history. [1]
October 14 – Miss Earth Vietnam 2023 held in Ho Chi Minh City; From October 20 – COVID-19 is no longer a particularly dangerous infectious disease (group A) October 29 – Decision 3983/QD-BYT, annulling 160 documents on COVID-19 epidemic prevention and control issued by the Ministry of Health, takes effect
However, another effect that plays a role is the +M effect which adds electron density back into the benzene ring (thus having the opposite effect of the -I effect but by a different mechanism). This is called the mesomeric effect (hence +M) and the result for fluorine is that the +M effect approximately cancels out the -I effect.
Sydnone structures are mesoionic. In chemistry, mesoionic compounds are one in which a heterocyclic structure is dipolar and where both the negative and the positive charges are delocalized. [1]
15 February – Vietnam lifts its COVID-19-related curbs on international passenger flights with no limitation on the number of flights in order to restore the travel to pre-pandemic level. [ 2 ] 6 September – A karaoke bar fire near Ho Chi Minh City kills at least 32 people.
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