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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.
[[Image:Ambrose Everett Burnside.jpg|240px|thumb|right|Portrait of Ambrose Burnside by [[Mathew Brady]], ca. 1860]]
'''Ambrose Everett Burnside''' ([[May 23]], [[1824]] – [[September 13]], [[1881]]) was a [[Union Army]] [[general]] in the [[American Civil War]] and a politician from [[Rhode Island]].
*Examples of -M substituents: [[acetyl]] (UPAC ethanoyl) - [[nitrile]] - [[nitro]]
==Pre Civil War==
*Examples of +M substituents: [[alcohol]] - [[amine]]
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).
Burnside graduated from the [[U.S. Military Academy]] in [[1847]] and served in the [[Mexican-American War]] and [[Indian Wars]]. He resigned in [[1852]] to manufacture a [[breech-loading rifle]] of his own invention; he settled in Rhode Island but failed to gain a government contract and had to assign his patent to creditors. During this period he was also a major general in the state militia. With the outbreak of the Civil War he raised a regiment of which he was appointed [[colonel]].
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.
==Civil War==
== External links==
Burnside commanded a brigade at [[First Bull Run]] and commanded the [[North Carolina]] Expeditionary Corps, which formed the nucleus for the [[IX Corps (ACW)|IX Corps]]. For his successes at [[Battle of Roanoke Island|Roanoke Island]] and [[Battle of New Bern|New Bern]] he was promoted to [[major general]] and offered command of the [[Army of the Potomac]] following [[George McClellan]]'s failure in the [[Peninsula Campaign]]. Refusing this, he detached part of his corps to the aid of [[John Pope (military officer)|John Pope]] in the [[Second Bull Run]] Campaign. Again offered command following that debacle, Burnside again declined and was given command of the [[I Corps (ACW)|I]] and IX Corps during the [[Maryland]] operations. He fought at [[Battle of South Mountain|South Mountain]] and then at the [[Battle of Antietam]], where his two corps were placed on opposite ends of the Union battle line. He nonetheless remained in wing command over the IX Corps—a cumbersome arrangement that may explain his slowness in attacking at “Burnside Bridge”. The delay allowed [[A.P. Hill]]'s [[Confederate]] division to come up from [[Harpers Ferry]] and repulse the Union breakthrough.
* IUPAC [[Gold Book]] [http://www.iupac.org/goldbook/M03844.pdf definition]
==Fredericksburg See also ==
* [[List of publications in chemistry#Organic chemistry|Important publications in organic chemistry]]
== References ==
With McClellan's removal after Antietam, Burnside was assigned to command the Army of the Potomac. He reluctantly obeyed this order. On [[November 14]], [[1862]], President [[Abraham Lincoln]] approved General Burnside's plan to capture the [[Confederate]] capital at [[Richmond, Virginia]]. This plan led to a dramatic Union defeat at the [[Battle of Fredericksburg]] on [[December 13]] that year. His advance upon Fredericksburg was rapid, but later delays, due to poor planning in marshalling pontoon bridges for crossing the [[Rappahannock River]], allowed [[Robert E. Lee]] to concentrate along Marye's Heights just west of town and easily repulse the Union attacks. Attacks south of town, which were supposed to be the main avenue of attack, were also mismanaged and Union breakthroughs went unsupported. Upset by the failure of his plan, Burnside declared that he himself would lead an assault by his old corps. He was talked out of it, but relations between the commander and his subordinates were strained. Accepting full blame, he resigned from his command as head of the Army of the Potomac; he offered to retire completely from the [[U.S. Army]], but this was refused.
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[[Category:Chemical bonding]]
In [[January]], [[1863]], Burnside launched a second offensive against Lee, but it bogged down in winter rains before it accomplished anything and has been derisively called the [[Mud March]]. In its wake he asked that several officers be relieved of duty and court-martialed; he also offered to resign. Lincoln chose the latter option.
[[de:Mesomerer Effekt]]
==1863–1865==
Lincoln was unwilling to lose Burnside and assigned him to the Department of the Ohio. Here he dealt with [[copperhead]]s such as [[Clement Vallandigham]] and Confederate raiders such as [[John Hunt Morgan]]. In 1863 he advanced to [[Knoxville, Tennessee]], but after the Union defeat at the [[Battle of Chickamauga]], Burnside found the tables turned and he was besieged by [[James Longstreet]] in [[Chattanooga]]. The siege was raised by troops under [[William Tecumseh Sherman]] after [[Braxton Bragg]]'s defeat at [[Battle of Chattanooga|Chattanooga]].
Burnside was then ordered to take the IX Corps back to Virginia, where he fought in the [[Overland Campaign]] directly under [[Ulysses S. Grant]]; he was not assigned initially to the Army of the Potomac because he outranked its commander, Major General [[George G. Meade]]. (This cumbersome arrangement was rectified during the [[Battle of North Anna]] on [[May 25]], [[1864]], when his corps was placed under Meade.)
Burnside fought at the [[Battle of the Wilderness|Wilderness]] and [[Battle of Spotsylvania Court House|Spotsylvania]], where he performed in a mediocre manner, appearing reluctant to commit his troops to frontal assaults after the Fredericksburg experience. After North Anna and [[Battle of Cold Harbor|Cold Harbor]] he took his place in the siege lines at [[Siege of Petersburg|Petersburg]].
In [[July]], [[1864]], Burnside agreed to a plan suggested by a regiment of [[Pennsylvania]] coal miners in his corps: dig a mine under a fort in the Confederate entrenchments and place explosives there. The fort was destroyed and many rebels died in what is known as the [[Battle of the Crater]]. But through interference from Meade, Burnside was ordered not to use his division of black troops (specially trained for this mission) and had to use untrained white troops instead. Those troops, badly led by their commanders, entered the crater itself instead of going around the edge, and got caught in the hole, resulting in high casualties. Burnside got the blame for this failure and he was sent on leave and never recalled. He finally resigned his commission on [[April 15]], [[1865]].
==Post Civil War==
After his resignation Burnside was employed in numerous railroad and industrial directorships. During the course of his career, he was elected to three one-year terms as [[governor]] of Rhode Island ([[1866]]–[[1868]]). At its inception in 1871, the [[National Rifle Association]] chose him as that organization's first president.. During a visit to [[Europe]] in [[1870]] he tried to act as mediator between the French and the Germans in the [[Franco-Prussian War]], [[1870]]–[[1871|71]]. In [[1874]] he was elected a [[US Senator]] from Rhode Island and served until his death at [[Bristol, Rhode Island]], on [[September 13]], [[1881]]. He is buried in Swan Point Cemetery, [[Providence, Rhode Island]].
==Assessment==
Noted for his [[facial hair]], joining his ears to his moustache but with chin clean-shaven; the word ''burnsides'' was coined to describe these strips of hair in front of the ears. The syllables were later reversed to give ''[[sideburns]]''.
Personally, Burnside was always very popular—both in the army and in politics—but he was out of his depth as a senior army commander, a fact no one knew better than Burnside himself. Knowing his capabilities, he twice refused command of the Army of the Potomac until finally being forced under orders to accept it.
He died on September 13, 1881.
[[Category:1824 births|Burnside, Ambrose]]
[[Category:1881 deaths|Burnside, Ambrose]]
[[Category:American Civil War people|Burnside, Ambrose]]
[[Category:Governors of Rhode Island|Burnside, Ambrose]]
[[Category:U.S. Army generals|Burnside, Ambrose]]
[[Category:United States Senators|Burnside, Ambrose]]
[[Category:West Point graduates|Burnside, Ambrose]]
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