By R. Uruk. Franklin W. Olin College of Engineering.
The resonance explanation of the structure of benzene The resonance theory can be applied successfully to explain the structure of benzene generic 10 mg deltasone with visa. According to this theory (a) resonance forms are imaginary discount deltasone 20 mg fast delivery, not real; (b) resonance structures differ only in the positions of their electrons; (c) different resonance forms do not have to be equivalent; (d) the more resonance structures there are buy cheap deltasone 40mg on line, the more stable the molecule is; (e) whenever it is possible to draw two or more resonance structures of a molecule, none of the structures will be in complete agreement with the compound’s chemical and physical properties; (f) the actual molecule or ion is better represented by a hybrid of these structures; (g) whenever an equivalent resonance structure can be drawn for a molecule, the molecule (or hybrid) is much more stable than any of the resonance structures could be individually if they could exist. If we consider the Kekule´ structure of benzene, it is evident that the two proposed structures differ only in the positions of the electrons. Therefore, instead of being two separate molecules in equilibrium, they are indeed two resonance contributors to a picture of the real molecule of benzene. Thus, instead of drawing the benzene structure using alternative single and double bonds, a hybrid structure can be drawn as follows. Hybrid structure of benzene The hybrid structure of benzene is represented by inscribing a circle in the hexagon as depicted above. With benzene, the circle represents the six electrons that are delocalized about the six carbon atoms of the benzene ring. The resonance theory accounts for the much greater stability of benzene (resonance energy) when compared with the hypothetical 1,3,5-cyclohexa- triene. Therefore, the structure of benzene is not really a 1,3,5-cyclohex- atriene, but a hybrid structure as shown above. The molecular orbital explanation of the structure of benzene The bond angles of the carbon atoms in benzene are 120. All carbon atoms 2 are sp -hybridized, and each carbon atom has a single unhybridized p orbital 2 perpendicular to the plane of the ring. The carbon sp -hybridized orbitals overlap to form the ring of the benzene molecule. H H + + _ _ + + H _ H _ + + H _ _ H Doughnut-shaped cloud of π electrons Six p atomic orbitals, one from each carbon of the benzene ring, combine to form six p molecular orbitals. Three of the molecular orbitals have energies lower than that of an isolated p orbital, and are known as bonding molecular orbitals. Another three of the molecular orbitals have energies higher than that of an isolated p orbital and are called antibonding molecular orbitals. Stability of benzene Benzene has a closed bonding shell of delocalized p electrons. Therefore, in the case of cyclohexadiene, where there are two double bonds, the energy required for the hydrogenation can be calculated as 2 ÂÀ28:6 ¼À57:2 kcal/mol. In practice, the experimental value is quite close to this calculated value, and is À55. Due to this stabilization energy, benzene does not undergo similar reactions to a cycloalkene. Many benzene derivatives have trivial names, which may show no resemblance to the name of the attached substituent group, e. The three possible isomers of a disubstituted benzene are differentiated by the use of the names ortho, meta and para, abbreviated as o-, m- and p-, respectively. Br Br Br Br Br Br ortho-Dibromobenzene meta-Dibromobenzene para-Dibromobenzene If the two groups are different, and neither is a group that gives a trivial name to the molecule, the two groups are named successively, and the word 4. If one of the two groups is the kind that gives a trivial name to the molecule, then the compound is named as a derivative of this compound. If the groups are the same, each is given a number, the sequence being the one that gives the lowest combina- tion of numbers; if the groups are different, then the last-named group is understood to be in position 1, and the other numbers conform to this. If one of the groups that give a trivial name is present, then the compound is named as having the special group in position 1. Before we go into any details of such reactions, let us try to understand the following terms. An aromatic hydrocarbon with a hydrogen atom removed is called an aryl group, designated by ArÀÀ. The benzene ring with one hydrogen atom removed (C6H5ÀÀ) is called the phenyl group, designated by PhÀÀ. Electrophiles attack the p system of benzene to form a delocalized nonaromatic carboca- tion (arenium ion or s complex). Some speciﬁc examples of electrophilic substitution reactions of benzene are summarized below (see Chapter 5). A summary of these effects of substituents on reactivity and orienta- tion of electrophilic substitution of substituted benzene is presented below.
This study assessed the impact of two types of relaxation training on diﬀerent aspects of the stress response cheap deltasone 10 mg with mastercard. It is interesting as it allows an insight into how these diﬀerent aspects of stress may interrelate cheap deltasone 10mg free shipping. It also illustrates the impact of relaxation training on children who are a rarely studied subject group generic 40 mg deltasone overnight delivery. Aims The study aimed to explore the relative impact of two types of relaxation training on children’s physiological and self-report responses. The training types were progressive muscle relaxation and imagery based relaxation. Participants The study involved 64 children from a school in Germany who were aged between 10 and 12 years. Design The study used a randomized control trial design and participants were randomly allocated to one of three arms of the trial: progressive muscle relaxation, imagery based relaxation or the control group. The children were asked to sit quietly for ﬁve minutes (baseline period), then they took part in the intervention, the children were then asked to sit quietly again for ﬁve minutes (follow-up). Progressive muscle relaxation: Children were asked to tense and relax speciﬁc muscle groups for a period of 7 minutes. These were hand muscles, arms, forehead, cheeks, chest, shoulders, stomach and thighs. Imagery based relaxation: Children in this group were asked to imagine that they were a butterﬂy going on a fantasy journey such as to a meadow, a tree or a boat. Control group: Children in this group listened to audiotapes of neutral stories which were designed not to elicit any feeling of either tension or relaxation. Subjective measurements were taken before and after the baseline period, after the intervention and after the follow-up period. Sensation of perceived calmness, subjective feeling of wellness, feeling of perceived attentiveness) and their physical well-being (e. Results The results were assessed to examine the impact of relaxation training regardless of type of relaxation and also to explore whether one form of relaxation training was more eﬀective. Physiological changes: The results showed that imagery relaxation was related to a decrease in heart rate and skin conductance but did not result in changes in skin tem- perature. In contrast, progressive muscle relaxation resulted in an increase in heart rate during the training session. Self report changes: The results showed increased ratings of mood and physical well- being during baseline and training sessions for all interventions. Conclusions The authors conclude that relaxation training can result in psychophysiological changes but that these vary according to type of training. What is also interesting, however, is the degree of variability between the diﬀerent measures of change. In particular, diﬀerences were found in the changes between diﬀerent aspects of the children’s physiology – a change in heart rate did not always correspond to a change in skin temperature. Further, changes in physiology did not always correspond to changes in self-reported mood or physical well-being. Therefore a measure indicating that heart rate had gone down did not always correspond with a self-report that the individual’s heart was more calm. Laboratory versus naturalistic research Laboratory research is artiﬁcial whereas real life research is uncontrolled. Some studies, however, illustrate high levels of congruence between physiological responses in the laboratory and those assessed using ambulatory machines in real life. However, other studies have found no relationship or only some relationship with some measures (e. In addition, they argued that appraisal is central to the congruence between laboratory and naturalistic measures and that higher congruence is particularly appar- ent when the stressors selected are appraised as stressful by the individual rather than identiﬁed as stressful by the researcher. This indicates that laboratory assessments may be artiﬁcial but do bear some resemblance to real life stress. Physiological versus self-report measures Stress is considered to reﬂect both the experience of ‘I feel stress’ and the underlying physiological changes in factors such as heart rate and cortisol levels. This question is central not only to stress research but also to an understanding of mind/body interactions. Research has addressed this association and has consistently found no or only poor relationships between physio- logical and perceived measures of stress (see Focus on research 10.
As a defense against fear of abandonment trusted 5 mg deltasone, borderline people are compulsively social generic 10mg deltasone amex. But their behaviors buy deltasone 20 mg online, including their intense anger, demands, and suspiciousness, repel people. These behaviors are designed to call forth a “saving‖ response from the other person. Borderline individuals also show disturbance in their concepts of identity: They are uncertain about self-image, gender identity, values, loyalties, and goals. They may have chronic feelings of emptiness or boredom and be unable to tolerate being alone. Some theories focus on the development of attachment in early childhood, while others point to parents who fail to provide adequate attention to the child‘s feelings. Others focus on parental abuse (both sexual and physical) in adolescence, as  well as on divorce, alcoholism, and other stressors (Lobbestael & Arntz, 2009). In comparison to the controls, the borderline patients showed relatively larger affective responses when they were attempting to quickly respond to the negative emotions, and showed less cognitive activity in the prefrontal cortex in the same conditions. People having antisocial personality disorder are sometimes referred to as “sociopaths‖ or “psychopaths. They lie, engage in violence against animals and people, and frequently have drug and alcohol abuse problems. They are egocentric and frequently impulsive, for instance suddenly changing jobs or relationships. The intensity of antisocial symptoms tends to peak during the 20s and then may decrease over time. Biological and environmental factors are both implicated in the development of antisocial  personality disorder (Rhee & Waldman, 2002). Twin and adoption studies suggest a genetic  predisposition (Rhee & Waldman, 2002), and biological abnormalities include low autonomic activity during stress, biochemical imbalances, right hemisphere abnormalities, and reduced gray matter in the frontal lobes (Lyons-Ruth et al. Environmental factors include neglectful and abusive parenting styles, such as the use  of harsh and inconsistent discipline and inappropriate modeling (Huesmann & Kirwil, 2007). What behaviors do they engage in, and why are these behaviors so harmful to them and others? Prevalence, correlates, and disability of personality disorders in the United States: Results from the national epidemiologic survey on alcohol and related conditions. Childhood sexual abuse in relation to neurobiological challenge tests in patients with borderline personality disorder and normal controls. A neurocognitive model of borderline personality disorder: Effects of childhood sexual abuse and relationship to adult social attachment disturbance. Emotional, cognitive and physiological correlates of abuse-related stress in borderline and antisocial personality disorder. The borderline diagnosis I: Psychopathology, comorbidity, and personality structure. Genetic and environmental influences on anti-social behavior: A meta-analysis of twin and adoptions studies. Genetic and environmental influences on anti-social behavior: A meta-analysis of twin and adoptions studies. Serotonin transporter polymorphism and borderline or antisocial traits among low-income young adults. Reduced prefrontal gray matter volume and reduced autonomic activity in antisocial personality disorder. This complexity of symptoms and classifications helps make it clear how difficult it is to accurately and consistently diagnose and treat psychological disorders. In this section we will review three other disorders that are of interest to psychologists and that affect millions of people:somatoform disorder, factitious disorder, and sexual disorder. Somatoform and Factitious Disorders Somatoform and factitious disorders both occur in cases where psychological disorders are related to the experience or expression of physical symptoms. The important difference between them is that in somatoform disorders the physical symptoms are real, whereas in factitious disorders they are not. One case in which psychological problems create real physical impairments is in the somatoform disorder known assomatization disorder (also called Briquet‘s syndrome or Brissaud- Marie syndrome). Somatization disorder is a psychological disorder in which a person experiences numerous long-lasting but seemingly unrelated physical ailments that have no identifiable physical cause. A person with somatization disorder might complain of joint aches, vomiting, nausea, muscle weakness, as well as sexual dysfunction.
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