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The '''mesomeric effect''' or '''resonance effect''' in [[chemistry]] is a property of [[substituent]]s or [[functional group]]s in a [[chemical compound]]. The effect is used in a qualitative way and describes the electron withdrawing or releasing properties of substituents based on relevant [[resonance structure]]s and is symbolized by the letter '''M'''. The mesomeric effect is negative ('''-M''') when the substituent is an electron-withdrawing group and the effect is positive ('''+M''') when based on resonance the substituent is an electron releasing group.
'''July 25''' is the 206th day (207th in [[leap year]]s) of the year in the [[Gregorian Calendar]], with 159 days remaining.
*Examples of -M substituents: [[acetyl]] (UPAC ethanoyl) - [[nitrile]] - [[nitro]]
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*Examples of +M substituents: [[alcohol]] - [[amine]]
==Events==
*[[306]] - [[Constantine I of the Roman Empire|Constantine I]] proclaimed [[Roman Empire|Roman]] emperor by his troops.
*[[1261]] - [[Constantinople]] is captured by [[Nicaean Empire|Nicaean]] forces under the command of [[Michael VIII Palaeologus]], allowing the re-creation of the [[Byzantine Empire]].
*[[1567]] - Don Diego de Losada founds the city of Santiago de Leon de Caracas, modern-day [[Caracas]], the capital city of [[Venezuela]].
*[[1593]] - [[Henry IV of France]] publicly converts from [[Protestantism]] to [[Roman Catholic]]ism.
*[[1722]] - [[Three Years War]] begins along [[Maine]] and [[Massachusetts]] border.
*[[1758]] - [[French and Indian War]]: The island battery at [[Fortress Louisbourg]] is silenced and all [[France|French]] warships are destroyed or taken.
*[[1759]] - French and Indian War: In [[Canada]], British forces capture [[Fort Niagara]] from French, who subsequently abandon [[Fort Rouillé]].
*[[1799]] - At [[Aboukir]] in [[Egypt]], [[Napoleon I of France]] defeats 10,000 [[Ottoman Empire|Ottomans]] under [[Mustafa Pasha (Egypt)|Mustafa Pasha]].
*[[1814]] - [[War of 1812]]: [[Battle of Lundy's Lane]] - Reinforcements arrive near [[Niagara]] for General Riall's [[United Kingdom|British]] and [[Canada|Canadian]] force, and bloody, all-night battle with [[Jacob Brown]]'s [[United States|American]]s commences at 18.00; Americans retreat to [[Fort Erie]].
*[[1853]] [[Joaquin Murietta]] famous [[Californio]] bandit, is killed
*[[1861]] - [[American Civil War]]: The [[Crittenden-Johnson Resolution]] is passed by the [[Congress of the United States|U.S. Congress]] stating that the war is being fought to preserve the [[United States|Union]] and not to end [[slavery]].
*[[1866]] - The [[Congress of the United States|U.S. Congress]] passes legislation authorizing the rank of [[General of the Army]] (now called "5-star general") Lieutenant General [[Ulysses S. Grant]] becomes the first to have this rank.
*[[1868]] - [[Wyoming]] becomes a [[Political divisions of the United States|United States territory]].
*[[1897]] - Writer [[Jack London]] sails to join the [[Klondike Gold Rush]] where he will write his first successful stories.
*[[1898]] - The [[United States]] invasion of [[Puerto Rico]] begins with U.S. troops landing at [[Guánica Bay]].
*[[1907]] - [[Korea]] becomes a [[protectorate]] of [[Japan]].
*[[1909]] - [[Louis Bleriot]] makes the first flight across the [[English Channel]] in a heavier-than-air machine ([[Calais]] to [[Dover, England|Dover]] in 37 minutes).
*[[1917]] - Sir [[Thomas Whyte]] introduces the first [[income tax]] in [[Canada]] as a "temporary" measure (lowest bracket is 4% and highest is 25%).
*[[1920]] - [[Telecommunications]]: first transatlantic two-way [[radio]] broadcast.
*[[1934]] - [[Nazi]]s assassinate [[Austria]]n Chancellor [[Engelbert Dollfuss]] in a failed coup attempt.
*[[1943]] - [[World War II]]: [[Benito Mussolini]] is forced out of office by his own [[Italy|Italian]] Grand Council and is replaced by [[Pietro Badoglio]].
*[[1944]] - World War II: [[Operation Spring]] - One of the bloodiest days for [[Canada|Canadian]]s during the war: 18,444 casualties, including 5,021 killed.
*[[1946]] - [[Nuclear testing]]: In the first underwater test of the [[atomic bomb]], the surplus [[USS Saratoga (CV-3)|USS Saratoga]] is sunk near [[Bikini Atoll]] in the [[Pacific Ocean]] when the [[United States]] detonates the "[[Baker Day]]" device.
* 1946 - At Club 500 in [[Atlantic City, New Jersey]], [[Dean Martin]] and [[Jerry Lewis]] stage their first show as a [[comedy]] team.
*[[1952]] - [[Puerto Rico]] becomes a self-governing commonwealth of the [[United States]].
*[[1956]] - 45 miles south of [[Nantucket Island]], the Italian ocean liner [[SS Andrea Doria|SS Andrea Doria]] sinks after colliding with the [[SS Stockholm|SS Stockholm]] in heavy [[fog]], killing 51.
*[[1969]] - [[Vietnam War]]: US President [[Richard Nixon]] declares the [[Nixon Doctrine]] stating that the [[United States]] now expects its [[Asia]]n allies to take care of their own military defense. This was the start of the "Vietnamization" of the war.
*[[1973]] - [[Soviet Union|Soviet]] [[Mars 5]] space probe launched.
*[[1976]] - The first performance of the [[Philip Glass]] [[opera]] ''[[Einstein on the Beach]]''
*[[1977]] - A supposed [[thunderbird (cryptozoology)|thunderbird]] is reported attacking a boy named Marlon Lowe.
*[[1978]] - The first so-called [[in-vitro fertilization | test-tube baby]], [[Louise Brown]], is born.
*[[1984]] - [[Salyut 7]] Cosmonaut [[Svetlana Savitskaya]] becomes the first woman to perform a [[space walk]].
*[[1989]] - [[Rock and roll|Rock]]/[[Hip-hop]] trio [[The Beastie Boys]] release the classic ''[[Paul's Boutique]].''
*[[1990]] - Comedian [[Roseanne Barr]] grabs her crotch and spits on the ground when performing the [[U.S.]] national anthem at a [[San Diego Padres]] game.
*[[1994]] - [[Israel]] and [[Jordan]] sign the [[Washington Declaration]] which formally ends the [[state of war]] that has existed between the nations since [[1948]].
*[[1997]] - [[K.R. Narayanan]] is sworn-in as [[India]]'s 10th president and the first member of the [[Dalits caste]] to hold this office.
*[[1998]] - The [[United States Navy]] commissions the aircraft carrier [[USS Harry S. Truman|USS Harry S. Truman]] and puts her into service.
*[[2000]] - An [[Air France]] [[Concorde]] supersonic passenger jet crashes just after takeoff from [[Paris]] killing all 109 aboard and 5 on the ground.
*[[2004]] - [[Lance Armstrong]] makes history, winning his 6th (consecutive) [[Tour de France]].
* 2004 - Over 100,000 opponents to [[Israel's unilateral disengagement plan of 2004]] participate in a [[human chain]] from [[Gush Katif]] (The Jewish communities adjacent to the [[Gaza Strip]], [[Israel]]), to the [[Western Wall]], [[Jerusalem]] (90 kilometers).
The net electron flow from or to the substituent is determined also by the [[inductive effect]]. It's important to note that the mesomeric effect as a result of p - orbital overlap (resonance) has absolutely no effect on this inductive effect, as the inductive effect is purely to do with the [[electronegativity]] of the atoms and their structural chemistry (which atoms are connected to which).
==Births==
*[[1109]] - [[Afonso I of Portugal|Afonso, first king of Portugal]]
*[[1562]] - [[Kiyomasa Kato|Kato Kiyomasa]], Japanese daimyo and samurai (d. [[1611]])
*[[1799]] - [[David Douglas]], botanist, plant collector, explorer (d. [[1834]])
*[[1844]] - [[Thomas Eakins]], artist (d. [[1916]])
*[[1848]] - [[Arthur Balfour]], Prime Minister of the [[United Kingdom]] [[1902]]-[[1907]] (d. [[1930]])
*1848 - [[Ottokar Kernstock]], poet (d. [[1928]])
*[[1867]] - [[Max Dauthendey]], writer (d. [[1918]])
*[[1870]] - [[Maxfield Parrish]], illustrator (d. [[1966]])
*[[1883]] - [[Alfredo Casella]], [[Italy|Italian]] composer (d. [[1947]])
*[[1884]] - [[Davidson Black]], doctor of anatomy and physical anthropologist (d. [[1934]])
*[[1894]] - [[Walter Brennan]], [[Academy Award ]] winning actor (d. [[1974]])
*[[1902]] - [[Eric Hoffer]], philosopher (d. [[1983]])
*[[1905]] - [[Elias Canetti]], writer, recipient of the [[Nobel Prize in Literature]] [[1981]] (d. [[1994]])
*[[1906]] - [[Johnny Hodges]], saxophonist (d. [[1970]])
*[[1907]] - [[Karl Holler|Karl Höller]], composer (d. [[1987]])
*[[1920]] - [[Rosalind Franklin]], scientist (d. [[1958]])
*[[1924]] - [[Estelle Getty]], actress: "The Golden Girls"
*[[1929]] - [[Somnath Chatterjee]], politician, [[India]]
*[[1930]] - [[Maureen Forrester]], Canadian contralto, teacher
*[[1937]] - [[Colin Renfrew]], [[archeology]] professor
*[[1941]] - [[Marco Lucioni]], Italian painter
*[[1946]] - [[Rita Marley]], Jamaican-Cuban singer, widow of [[Bob Marley]]
*[[1948]] - [[Peggy Fleming]], [[figure skater]]
*[[1954]] - [[Walter Payton]], [[National Football League]] player (d. [[1999]])
*[[1955]] - [[Iman]], model
*[[1960]] - [[Alain Robidoux]], [[Canada|Canadian]] [[snooker]] player
*[[1967]] - [[Matt LeBlanc]], actor
*[[1977]] - [[Kenny Thomas]], [[NBA]] [[basketball]] player
*[[1978]] - [[Louise Brown]], first test tube baby
* 1978 - [[Gerard Warren]], [[American football]] player
*[[1979]] - [[Amy Adams]], American Idol 3 contestant
*[[1982]] - [[Brad Renfro]], actor
*1848 [[Ed Ashby]], firewalker
==Deaths==
*[[306]] - [[Constantius Chlorus]], [[Roman Emperors|Roman Emperor]]
*[[1492]] - [[Pope Innocent VIII]]
*[[1861]] - [[Jonas Furrer]], Swiss Federal Councilor (b. [[1805]])
*[[1834]] - [[Samuel Taylor Coleridge]], poet
*[[1853]] - [[Joaquin Murieta]], [[California]]n outlaw
*[[1887]] - [[John Taylor (1808-1887)|John Taylor]], American religious leader (b. [[1808]])
*[[1899]] - [[Theodore August Heintzman]], piano manufacturer
*[[1934]] - [[Engelbert Dollfuss]], [[Austria]]n politician
*[[1937]] - [[Edward Saunders]], agricultural scientist
*[[1958]] - [[Harold Warner]], one of the [[Warner Brothers]]
*[[1973]] - [[Louis Stephen St. Laurent]], twelfth [[Prime Minister of Canada]]
*[[1980]] - [[Vladimir Vysotsky]], [[Russia]]n [[bard (Soviet Union)|bard]] (poet, singer) and actor, (b. [[1938]])
*[[1997]] - [[Ben Hogan]], one of the world's best known golfers
*[[2003]] - [[Ludwig Bölkow]], airplane engineer
*2003 - [[John Schlesinger]], film director
The concepts of mesomeric effect, '''mesomerism''' and '''mesomer''' were introduced by [[Christopher Kelk Ingold|Ingold]] in 1938 as an alternative to the [[Linus Pauling|Pauling's]] synonymous concept of [[resonance effect|resonance]] <ref>''If It's Resonance, What Is Resonating?'' Kerber, Robert C. . J. Chem. Educ. '''2006''' 83 223. [http://www.jce.divched.org/Journal/Issues/2006/Feb/abs223.html Abstract]</ref>. Mesomerism is in this context is often encountered in German and French literature but in English literature the term resonance dominates.
==Holidays and observances==
*[[Roman festivals]] - ''[[Furinalia]]''
*[[Galiza]] - National Day (''Dia da Patria Galega'').
*[[Saint James the Great]] - patron saint of [[Spain]].
*[[Costa Rica]] - Anniversary of the Annexation of Guanacaste Province
*[[Cuba]] - Eve of Revolution Day
*[[Puerto Rico]] - Constitution Day (1952)
*[[Tunisia]] - Republic Day (1957)
*[[Virgin Islands]] - Hurricane Supplication Day
*[[Tahuantinsuyu|Inca]] - festival in honor of [[Ilyap'a]]
== External links ==
* IUPAC [[Gold Book]] [http://www.iupac.org/goldbook/M03844.pdf definition]
* [http://news.bbc.co.uk/onthisday/hi/dates/stories/july/25 BBC: On This Day]
== See also ==
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* [[List of publications in chemistry#Organic chemistry|Important publications in organic chemistry]]
== References ==
[[July 24]] - [[July 26]] - [[June 25]] - [[August 25]] -- [[historical anniversaries|listing of all days]]
<references />
[[Category:Chemical bonding]]
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