An Extension of the Hückel 4N + 2 Rule to Polycyclic Non-alternant Conjugated Hydrocarbons

1975 ◽  
Vol 53 (6) ◽  
pp. 945-951 ◽  
Author(s):  
Jerzy Kruszewski ◽  
Tadeusz Marek Krygowski
Keyword(s):  
Substituent Effects ◽  
General Rule ◽  
Electron System ◽  
Ionic Form ◽  
Conjugated Hydrocarbons ◽  
Benzene Rings ◽  
The Difference ◽  
Polycyclic Conjugated Hydrocarbons ◽  
Prediction Of Substituent Effects ◽  
Stability Indices

A general rule of aromatic stability of non-alternant polycyclic conjugated hydrocarbons has been detailed and using aromatic stability indices, corroborated. The π-electron system is said to be relatively more stable if the difference between number of 4N + 3-type rings minus number of 4N + 1-type rings is 0 or divisible by 4. If not, the system is assumed to be relatively unstable. The presence of benzene rings does not affect the rule. A further extension for intramolecular H-bonded systems is also suggested. The rule suggested permits prediction of substituent effects on stability as well as the ionic form being most stable if the rule is not fulfilled.

On the extension of the Hückel rule to polycyclic non-alternant conjugated hydrocarbons

1976 ◽  
Vol 54 (11) ◽  
pp. 1789-1794 ◽  
Author(s):  
I. Gutman ◽  
N. Trinajstić
Keyword(s):  
Electron System ◽  
The Other ◽  
Conjugated Hydrocarbons ◽  
General Rules ◽  
Stabilizing Effect ◽  
Hückel Rule ◽  
Polycyclic Conjugated Hydrocarbons ◽  
Theoretical Considerations ◽  
Conjugated Molecule

General rules for aromatic stability of non-alternant polycyclic conjugated hydrocarbons are obtained using graph–theoretical considerations. Every pair of odd-membered rings contained in the conjugated molecule has a stabilizing effect if one ring is of the size 4N + 1 and the other of the size 4N + 3. If both rings are of the size 4N + 1 or 4N + 3, a destabilizing effect occurs. This conclusion holds both for fused and disjointed rings. The π-electron System is said to be relatively more stable if the number of (4N + l)-membered rings is equal to the number of (4N + 3)-rings.

Nucleophilic cleavage of diaryl disulphides

1973 ◽  
Vol 26 (1) ◽  
pp. 121 ◽  
Author(s):  
DAR Happer ◽  
JW Mitchell ◽  
GJ Wright
Keyword(s):  
Transition State ◽  
Reaction Rate ◽  
Substituent Effects ◽  
Butyl Alcohol ◽  
Sulphur Atom ◽  
Cyanide Ion ◽  
Benzene Rings ◽  
Nucleophilic Cleavage ◽  
Rapid Equilibrium ◽  
Electron Withdrawal

The rates of cleavage of 14 symmetrically substituted diaryl disulphides by cyanide ion have been measured in 60% aqueous t-butyl alcohol at pH 9.2. A plot of log k against σ� shows that while the reaction rate is accelerated by inductive electron withdrawal from the benzene rings, substituents capable of conjugative interaction are not correlated by their σ� parameters. +R substituents cause reaction to occur much faster than predicted on the basis of their σ� values, while -R substituents react more slowly than predicted. Measurement of rates of cleavage of three series of unsymmetrically substituted disulphides by cyanide or hydroxide shows that these unusual substituent effects arise from substituents in the thiocyanate-forming aryl ring. This behaviour is explained in terms of a change in the electronic behaviour of the thio- cyanate-forming sulphur atom from -I, + R in the disulphide to -I,-R in the rate-determining transition state for the reaction. The study does not show whether the cleavage involves an SN2 process or rapid equilibrium formation of a pentacovalent intermediate.

scholarly journals Verifying the PCP-rule by five-center bond indices

2009 ◽  
Vol 74 (5) ◽  
pp. 549-554 ◽  
Author(s):  
Jelena Djurdjevic ◽  
Ivan Gutman ◽  
Robert Ponec
Keyword(s):  
Membered Ring ◽  
Energy Effect ◽  
Conjugated Hydrocarbons ◽  
Cyclic Conjugation ◽  
Bond Indices ◽  
Polycyclic Conjugated Hydrocarbons

According to the recently discovered PCP-rule, the (stabilizing) energy- effect of the cyclic conjugation in the 5-membered ring of acenaphthyleneand fluoranthene-type polycyclic conjugated hydrocarbons increases with the number of phenyl-cyclopentadienyl (PCP) fragments present in the molecule. It is now shown that the validity of the PCP-rule is also supported by the 5-center bond indices, an independent quantitative theoretical measure of cyclic conjugation in 5-membered rings.

scholarly journals INSECTICIDE APPLICATION SPEED IN THE CONTROL OF LEPIDOPTERAN PESTS IN SOYBEAN1

2020 ◽  
Vol 33 (1) ◽  
pp. 72-80
Author(s):  
LENIO CESAR MORAES DE CAMARGO ◽  
DANILO DE BRITO GARCIA ◽  
OTÁVIO JORGE GRÍGOLI ABI SAAB ◽  
AMARILDO PASINI ◽  
DANILO AUGUSTO SARTI ◽  
...  
Keyword(s):  
Chemical Control ◽  
General Rule ◽  
Leaf Damage ◽  
Application Technology ◽  
Spray Volume ◽  
The Difference ◽  
Soybean Plants ◽  
Efficacy Parameters ◽  
Great Damage ◽  
Chrysodeixis Includens

ABSTRACT During the chemical control of pests, diseases and weeds, great importance is given to the phytosanitary product and little attention to the application technology. The control of soybean pests did not escape the general rule and, therefore, some pests known as secondary, and even nonexistent, became responsible for great damage to the soybean crop. The objective of this work was to test the application of insecticide at different speeds (5 and 16 km h-1) by varying the rates of application in 108 to 110 and 199 to 216 L ha-1 to quantify the difference in the coverage percentage of the applied insecticide in the canopy of soybean plants, and to verify the interaction of these factors with efficacy parameters for the control of caterpillars (Helicoverpa armigera and Chrysodeixis includens). In general, the highest leaf coverage by the insecticide was observed in the upper part of the canopy, regardless of the rate and speed of application, resulting in lower leaf damage. For the middle and lower thirds of the plant, the decrease in speed influenced more the decrease in leaf damage by the caterpillars than the increase in the spray volume.

Integration of Predated Notifications of Personal Actions for HR-Planning in ERP-Systems

2012 ◽  
pp. 291-303 ◽  
Author(s):  
Peter Cissek ◽  
Jorge Marx Gomez
Keyword(s):  
Human Resource ◽  
Business Processes ◽  
Planning Process ◽  
Cost Savings ◽  
General Rule ◽  
Resource Planning ◽  
Erp Systems ◽  
Fully Integrated ◽  
Related Data ◽  
The Difference

This chapter intends to reveal the benefit of predated notifications of personal actions for HR-planning and discusses the interrelated demands on ERP-systems. If e-government is implemented, one has to think of rearranging the government’s HR-structure in order to adapt to the new circumstances, too. This means to take advantage of modern HR-methodology in order to become more efficient in HR-administration. One possible way in improving human resource management (HRM) is using predated notifications of personal actions for HR-planning. Human resource planning (HR-planning) is a component of strategic enterprise planning. It is fully integrated into the enterprise-wide planning process, because HR-planning is not only determined by other planning areas, but it also determines them vice versa. So the more precisely and comprehensively HR-planning is done, the more accurate derived key figures, which are used in other planning areas, can be. Governments usually deal with a huge amount of personnel, so HR is one of the main tasks in administration. Predated notifications of personal actions usually are known in present, but will be started in the future. In contrast to planning a personnel action the predated one will take place with the highest possible probability. An example for making the difference more clear may be an employee’s retirement. It does not stringently depend on the employee’s age, but rather on the person’s individual decision to retire. As a general rule, an employee’s intention to retire is already known about half a year before it takes place. If this information is used in the planning process, the company will have enough time to estimate the loss of knowledge or the cost-savings that will be caused by the employee’s withdrawal. In huge companies, HRM typically is supported by ERP-systems. The functionality offered by the software depends on the company’s needs and may range from a simple keeping of personnel data to a complex module called human capital management, which is used for payroll accounting, talent management, employee self services, and many more. If the decision-making body considers the company’s personnel as business critical, a lot of employee-related data is collected and analyzed, ranging from master data to planning key figures. This chapter will emphasize the importance of efficient HR-planning for governments in order to improve their business processes. It can be seen as one of the goals of e-government. It will be pointed out how HR-planning can be improved by using predated notifications of personal actions, so that HR-divisions in governments can use advanced HR-planning right on from the beginning when preparing themselves for e-government.

A theoretical study on a series of polycyclic conjugated hydrocarbons—dinaphthobenzo[1,2:4,5]dicyclobutadienes with tunable charge transport properties by controlling [N]phenylenes and (anti)aromaticity

2019 ◽  
Vol 7 (22) ◽  
pp. 6721-6727
Author(s):  
Hang Yin ◽  
Daoyuan Zheng ◽  
Yan Qiao ◽  
Xiaofang Chen
Keyword(s):  
Charge Transport ◽  
Transport Properties ◽  
Theoretical Study ◽  
Energy Gap ◽  
Conjugated Hydrocarbons ◽  
Polycyclic Conjugated Hydrocarbons

A multi-dimensional relationship founded on the targeted [N] number, the energy gap (Eg) and the aromatic degree was constructed for predicting cyclobutadienoid-containing dinaphthobenzo[1,2:4,5]dicyclobutadienes (DNBDCs) with better charge transport properties.

The log kexovs. log kendo correlation as a mechanistic criterion; on the mechanisms of solvolysis of norbornyl derivatives and base-catalyzed isotope exchange of norbornanones

1976 ◽  
Vol 54 (5) ◽  
pp. 678-684 ◽  
Author(s):  
Sujit Banerjee ◽  
Nick Henry Werstiuk
Keyword(s):  
Transition State ◽  
Exchange Rates ◽  
Isotope Exchange ◽  
Transition States ◽  
Substituent Effects ◽  
Proton Exchange ◽  
Hydrogen Deuterium Exchange ◽  
Rate Data ◽  
Hydrogen Deuterium ◽  
The Difference

Rate data for the acetolysis of exo-norbornyl-sulfonates have been correlated with those for the corresponding endo isomers. It is shown that the slopes of the log kexovs. log kendo plots reflect the difference in delocalization between the transition states derived from the exo and endo isomers, respectively. The log kexovs. log kendo plot, which is comprised of the parent norbornyl sufonate and its derivatives substituted at the 5, 6, and 7 positions, has a slope of 1.11 ± 0.08, which establishes that σ bridging is absent in the transition state obtained from the exo isomer. A similar analysis of base-catalyzed hydrogen–deuterium exchange rates of norbornanones reveals that exo proton exchange is more sensitive to substituent effects than the corresponding endo process.

Aromaticity of Polycyclic Conjugated Hydrocarbons

ChemInform ◽  
2003 ◽  
Vol 34 (48) ◽  
Author(s):  
Milan Randic
Keyword(s):  
Conjugated Hydrocarbons ◽  
Polycyclic Conjugated Hydrocarbons
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