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Topic: Resonance structure

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	Tutorials: Drawing Resonance Structures
		Resonance structures are simply alternate Lewis structures for a given ion or molecule.
		Structures I and J are both acceptable resonance contributors for bisulfate ion, the conjugate base of sulfuric acid.
		Structure J is the more important resonance structure because it maximizes the number of covalent bonds and minimizes the number atoms with a nonzero formal charge.
	web.chem.ucla.edu /~harding/tutorials/resonance/draw_res_str.html (1694 words)

	Resonance (chemistry) - Wikipedia, the free encyclopedia
		Resonance structures are diagrammatic tools in organic chemistry to symbolize resonant bonds between atoms in molecules.
		Resonance structures all have the same chemical formula and same general shape.
		For example, for benzene rings, the alternating structure of double bonds in the ring structure are often drawn as a circle.
	en.wikipedia.org /wiki/Resonance_structure (594 words)

	General Chemistry at Penn State: Tutorials (Site not responding. Last check: 2007-11-01)
		The resonance structures are obtained by assigning one electron pair of the double bond to oxygen or carbon.
		Structures in which the second row atoms (B, C, N, O, F) have filled their valence shells (the octet rule) are generally more important than structures where the octet rule is not satisfied.
		Structures with strongly distorted bond angles and lengths are not important (application of this rule requires knowledge of molecular geometry, a topic to be covered latter).
	courses.chem.psu.edu /chem12/spring/tutorials/Lewis-struct.htm (1890 words)

	Chapter 8, Section 7 (Site not responding. Last check: 2007-11-01)
		The description of a molecule as a blend of different resonance structures is similar to the description of a paint color as a blend of primary colors.
		In writing resonance structures, the same atoms must be bonded to one another in all structures, so that the only differences are in the arrangements of electrons.
		To emphasize the resonance between two Lewis structures, benzene is often represented as a hexagon with a circle in it.
	cwx.prenhall.com /bookbind/pubbooks/blb/chapter8/medialib/blb0807.html (915 words)

	Modulenet
		Let’s look at a common example of resonance from general chemistry, the carbonate ion, CO As you work through the rules for drawing Lewis structures you get to the point where the octets of the peripheral atoms have been completed but the octet for carbon is not complete.
		Resonance structures for radicals involve pushing single electrons which is indicated by single-headed arrows.
		The resonance hybrid is a weighted average of all the contributing resonance structures.
	chemistry.armstrong.edu /P1/Modulenet.html (448 words)

	RESONANCE STRUCTURES (Site not responding. Last check: 2007-11-01)
		Resonance structures may differ in which atoms bear a formal charge, and in how many atoms bear formal charge, but the overall charge on a structure must be the same for all members of a set.
		The actual structure may be drawn with partial bonds and partial charges on atoms, while each resonance structure is drawn with full bonds and unit charges.
		The actual structure may be considered as a "weighted average" of the contributing resonance structures, with the more stable resonance structures making the greatest contribution to the overall structure.
	www.muhlenberg.edu /depts/chemistry/chem201woh/RESSTRS.html (312 words)

	Molecular Structure & Bonding
		In the formula on the right all four 1º-carbons are structurally equivalent (remember the tetrahedral configuration of tetravalent carbon); however the central formula has two equivalent 1º-carbons (bonded to the 3º carbon on the left end) and a single, structurally different 1º-carbon (bonded to the 2º-carbon) at the right end.
		Although structural formulas are essential to the unique description of organic compounds, it is interesting and instructive to evaluate the information that may be obtained from a molecular formula alone.
		The double bonded structure is regarded as the major contributor, the middle structure a minor contributor and the right hand structure a non-contributor.
	www.cem.msu.edu /~reusch/VirtualText/intro3.htm (3290 words)

	Resonance
		Draw the skeletal structure, using solid lines for the bonds that are found in all of the resonance structures.
		Resonance is possible whenever a Lewis structure has a multiple bond and an adjacent atom with at least one lone pair.
		The first Lewis structure is reasonable, but the second one, with three bonds and a lone pair on an oxygen atom, is not considered a reasonable resonance structure.
	www.mpcfaculty.net /mark_bishop/resonance.htm (1194 words)

	CHAPTER 6 Tutorial IV: Advanced Structure Elucidation
		All structures have the correct number of carbons and nitrogens, correct atom valences, and explain the observed HSQC and HMBC correlations within the specified limits.
		Oxygen atoms are placed in the structure to minimize the differences between observed and predicted carbon chemical shifts, and the resulting structures are sorted by shift agreements.
		The top structure is the most likely one and it agrees with the complete strychnine structure shown at the beginning of this tutorial.
	www.sciencesoft.net /NMRanalyst_Manual/HTML/tutorial_IV.html (1477 words)

	Leading Question (Site not responding. Last check: 2007-11-01)
		Resonance is the main structural feature of 9 that makes it a more stable isomer than 7, explaining its favorable formation as the product (76% yield).
		The resonance structures of quinazolinone 9 are highly favorable because one of the resonance structures, although it has a separation of charge, produces two 6-membered aromatic rings.
		Slight hydrogen bonding that possibly occurs between the ester group and the nitrogen-bound hydrogen may compensate for the sterically unfavorable proximity of the nitrogen-protecting group to the rest of the molecule.
	www.umich.edu /~chemh215/W02HTML/SSG6/ssg4/question/leadingq.html (326 words)

	chapter 8
		The Trojans are in a 1/1 resonance with Jupiter.
		In contrast, the resonance between the Saturnian satellites Tethys and Mimas is dependent on the inclination of the orbits, and the resonance is related to the nodes.
		The spin period of Venus is supposedly in a 5/4 resonance with the orbital period of the Earth as seen from Venus (Dyce and Pettengill, 1967; Goldreich and Peale, 1968).
	history.nasa.gov /SP-345/ch8.htm (4832 words)

	Chapter 11 (Site not responding. Last check: 2007-11-01)
		In this case, the structure is most representive of the real structure and resonance is not important.
		From the resonance structures shown in the textbook, it should be clear that the conjugated diene system, which we will say covers carbons 1, 2, 3, and 4 (and can be a part of a larger system), have slightly different bond lengths than we would expect from the classical model.
		One of the resonance structures shows this as a double bond and its contribution is responsible for this.
	www-ec.njit.edu /~skawinsk/chem243/chap11/chap11.htm (2207 words)

	Solutions to Quiz 1 Part II (Site not responding. Last check: 2007-11-01)
		To be resonance structures, the structures must have the same number of electrons and the atoms must be in the same position.
		Structure B is a structural isomer (not a resonance isomer) because the central atoms are different.
		Structure D does not have an octet around the Carbon atom, so this is not a good resonance structure.
	web.uccs.edu /chemistry/organic_online/quiz1solution.htm (175 words)

	Mar 26 HW
		From the resonance structures below, we can see that in compound (c) the negative charge may be moved onto the oxygen in the nitro group.
		Compound (b) does not have an analogous resonance structure; we can't draw a structure that shows the negative charge moving onto the nitro group.
		The first structure is most stable because it minimizes charge separation; the formal charge of all atoms is zero.
	cas.bellarmine.edu /chem117a/topics/mar26.htm (403 words)

	Physical Properties 2 (Site not responding. Last check: 2007-11-01)
		For esters and carboxylic acids, the appropriate resonance structures are shown in Figure 2.12.
		As in the case of the resonance structure with the C=N+HR linkage for amides, the resonance structure with the C=O+R linkage (R=H in carboxylic acids and R=alkyl, aryl, etc. in esters) is expected to be the minor contributor in esters and carboxylic acids due to the formal positive charge on the highly electronegative O atom.
		Note that stabilization may be afforded by the resonance structure involving a formal positive charge on the O bonded to H; by electronegativity considerations we expect that this structure will be a minor contributor.
	www.chem.wisc.edu /~newtrad/currref/AIDStopic/AIDStext/AIDSpp2.html (1869 words)

	Skill Development Exercises for Part C (Site not responding. Last check: 2007-11-01)
		Each second order resonance structure has an arrangement of electrons with more "hot spots" of + or - charge, and are therefore less favorable arrangements of the electrons.
		Any resonance structure in which two + charges are next to each other is very unfavorable.
		In a way, the meta intermediate has three good resonance structures, whereas the para intermediate has two good resonance structures and one bad resonance structure.
	home.earthlink.net /~cuachemistry/organic/SDEAns/AnsSDE29C.htm (906 words)

	Skill Development Exercises for Part B (Site not responding. Last check: 2007-11-01)
		For each set of resonance structures in SDE 3 (above) use curved arrows to show the movement of electrons that would accompany imaginary (infinitely fast) conversion of one resonance structure to the next (exclude crossed out structures).
		Resonance structures are imaginary and we can, in our minds, number the carbons 1-5, andÝ say that Resonance structures I and III are different (RS I has a -charge on C
		We will learn later that resonance structure II is not as important as I or III, so the experimental ratio would likely be even more skewed toward Product A.
	www.beloit.edu /~chem/Chem230/SDEANS/ANS3B/ANS3B.HTM (341 words)

	contact3
		I drew dioxin on the board and drew a resonance structure in which one of the oxygens had two double bonds to it and a +2 charge.
		There was a benzene structure in the molecule as well and I asked the student to draw a resonance structure as we did in class.
		The student did this and then I asked which was a greater resonance contributor, the structure that was just drawn (resonance with benzene) or one with an O with a negative charge and an N with a positive charge.
	www.umich.edu /~csie/undergraduate/jason/program/contact3 (2314 words)

	[No title] (Site not responding. Last check: 2007-11-01)
		For the structure on the right (the less stable structure): FC (carbon) = 4 -3 - 0 = +1 FC (oxygen) = 6 - 1 - 6 = -1 In both structures, the sum of the formal charges is zero.
		Neither structure alone is adequate to explain all of the properties and behaviors of the compound.
		The true structure is a hybrid of the two resonance structures with a greater contribution from the more stable structure.
	www.wfu.edu /~jonespb/review.doc (1869 words)

	Lewis Dot Structures Copy Right by C. Chieh, UoWaterloo
		Lewis dot structures are useful in explaining the chemical bonding in molecules or ions.
		For resonance structures, the skeleton of the molecule (or ion) stays in the same relative position, and only distributions of electrons in the resonance structures are different.
		In structures 2 and 3, the formal charges are +1 for S, and -1 for the oxygen atom with a single bond to S. The low formal charges of S make structures 2 and 3 more stable or more important contributors.
	www.science.uwaterloo.ca /~cchieh/cact/c120/dotstruc.html (1561 words)

	Skill Development Exercises-CA10 (Site not responding. Last check: 2007-11-01)
		An additional resonance structure (even if it is not very favorable) can only “help” lower the potential energy of a species.
		The resonance structures below show that the negative charge that results from loss of an H is spread out over 3 very electronegative oxygens.
		This extra resonance structure tell us that this conjugate base is lower in potential energy.
	home.earthlink.net /~cuachemistry/organic/SDEAns/Ans10.htm (1500 words)

	Energy Citations Database (ECD) - Energy and Energy-Related Bibliographic Citations
		We present experimental verification of predicted resonance structure in the energy dependence of the H+D{sub 2} reaction.
		Specifically we predict and observe a broad resonance in the H+D{sub 2}{yields}HD(v{sup '}=0, j{sup '}=7)+D reaction at a collision energy of 0.94 eV.
		This resonance structure is roughly Gaussian with a full width at half maximum of 0.1 eV.
	www.osti.gov /energycitations/product.biblio.jsp?osti_id=20216435 (208 words)

	[No title] (Site not responding. Last check: 2007-11-01)
		Using the resonance structure you have drawn, predict the shape, i.e.
		Draw your predicted structure using solid lines, dashed lines and wedges and describe the shape using such terms as linear, nonlinear, planar, non planar, and tetrahedral.
		Both resonance structures have the same number of bonds but the circled structure does not have the separation of unlike charges (c) Bonus question.
	www.sinc.sunysb.edu /Class/che112/exams/Q1s02Ans.doc (500 words)

	Beyond the Point Particle - An Electron Wave Structure (Site not responding. Last check: 2007-11-01)
		The correctness of this structure is supported by the physical laws which originate from this wave structure, including quantum theory, special relativity, electric force, gravity, and magnetism.
		The Space Resonance structure is obtained from three assumptions or principles: (1) a wave equation describing spherical scalar waves, (2) theSpace Density Assumption, which leads to an energy exchange mechanism, and (3) the Minimum Amplitude Principle, which regulates particle interactions.
		The resonance is composed of a spherical IN wave which converges to the center and an OUT wave which diverges from the center.
	www.quantummatter.com /body_point.html (6782 words)

	RESONANCE Fee Structure - Academic Year 2006-2007
		If a student fails to deposit the Course Fees (any Installment) including penalty even up to 4-weeks from the date of Installment; his/her admission may be cancelled with immediate effect.
		Old students of RESONANCE who have promoted from XI (VIKAAS, VIPUL) to XII (VIJETA) need not to pay Caution Money again; if they have not taken its refund in the past.
		Hence, the amount may increase or decrease in future and shall be passed on the students accordingly.
	www.resonance.ac.in /FeeStructure.asp (447 words)

	Resonance Structures (Site not responding. Last check: 2007-11-01)
		These Lewis structures are equivalent except for the placement of the electrons (i.e.
		This indicates that the ozone molecule is described by an average of the two Lewis structures (i.e.
		We draw two Lewis structures (in this case) because a single structure is insufficient to describe the real structure
	wine1.sb.fsu.edu /chm1045/notes/Bonding/Resonan/Bond07.htm (305 words)

	[No title] (Site not responding. Last check: 2007-11-01)
		Correct skeletal structure: ____________________________________________ B. Draw the Lewis structure for disulfur monoxide showing resonance structures (if appropriate).
		C. If resonance structures can be drawn for disulfur monoxide, determine the resonance structure(s) that contribute(s) most significantly to the actual structure of the molecule.
		Most significant resonance structure(s): ________________________________________ D. What is the name of the shape of the molecule?
	webpub.alleg.edu /employee/n/nlowmast/F2001ExamII.doc (381 words)

	$NRTSTR Tutorial (Site not responding. Last check: 2007-11-01)
		To characterize a chemical reaction at the electronic level along a chosen reaction coordinate s, one must therefore describe the continuous electronic redistribution from the reactant-like to product-like bonding pattern.
		In the transition state region, both R and P bonding patterns are expected to serve as "reference structures" in the 2-reference NRT expansion.
		In order to avoid the discontinuities that accompany promotion of a structure from secondary to reference status, it is necessary to specify that both the R and P structures be chosen as reference structures at every point.
	www.chem.wisc.edu /~nbo5/tut_nrt.htm (919 words)

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