Introduction to Organic Chemistry

Introduction

Chemical reactions involve the making and breaking of bonds. It is essential that we know what bonds are before we can understand any chemical reaction. To understand bonds, we will first describe several of their properties. The bond strength tells us how hard it is to break a bond. Bond lengths give us valuable structural information about the positions of the atomic nuclei. Bond dipoles inform us about the electron distribution around the two bonded atoms. From bond dipoles we may derive electronegativity data useful for predicting the bond dipoles of bonds that may have never been made before.
From these properties of bonds we will see that there are two fundamental types of bonds--covalent and ionic. Covalent bonding represents a situation of about equal sharing of the electrons between nuclei in the bond. Covalent bonds are formed between atoms of approximately equal electronegativity. Because each atom has near equal pull for the electrons in the bond, the electrons are not completely transferred from one atom to another. When the difference in electronegativity between the two atoms in a bond is large, the more electronegative atom can strip an electron off of the less electronegative one to form a negatively charged anion and a positively charged cation. The two ions are held together in an ionic bond because the oppositely charged ions attract each other as described by Coulomb's Law.

Ionic compounds, when in the solid state, can be described as ionic lattices whose shapes are dictated by the need to place oppositely charged ions close to each other and similarly charged ions as far apart as possible. Though there is some structural diversity in ionic compounds, covalent compounds present us with a world of structural possibilities. From simple linear molecules like H2 to complex chains of atoms like butane (CH3CH2CH2CH3), covalent molecules can take on many shapes. To help decide which shape a polyatomic molecule might prefer we will use Valence Shell Electron Pair Repulsion theory (VSEPR). VSEPR states that electrons like to stay as far away from one another as possible to provide the lowest energy (i.e. most stable) structure for any bonding arrangement. In this way, VSEPR is a powerful tool for predicting the geometries of covalent molecules.

The development of quantum mechanics in the 1920's and 1930's has revolutionized our understanding of the chemical bond. It has allowed chemists to advance from the simple picture that covalent and ionic bonding affords to a more complex model based on molecular orbital theory. Molecular orbital theory postulates the existence of a set of molecular orbitals, analogous to atomic orbitals, which are produced by the combination of atomic orbitals on the bonded atoms. From these molecular orbitals we can predict the electron distribution in a bond about the atoms. Molecular orbital theory provides a valuable theoretical complement to the traditional conceptions of ionic and covalent bonding with which we will start our analysis of the chemical bond..

Terms

Anion - A negatively charged ion.

Bond - That which holds together atoms in molecules and ions in lattices.

Cation - A positively charged ion.

Coulomb's Law - A mathematical formula whose consequence is that negatively and positively charged particles attract each other and similarly charged species repel each other.

Covalent Bond - A bond that results from a sharing of electrons between nuclei.

Ion - A charged species created by the gain or loss of an electron from an atom or neutral molecule.

Ionic Bond - A bond that results from electrostatic attraction between oppositely charged ions. The cation is positively charged, while the anion is negatively charged.

Lattice - A regularly repeating three-dimensional array of atoms, molecules, or ions.

Molecular Orbital - A combination of atomic orbitals in molecular orbital theory that provides an orbital description of a molecule analogous to the atomic orbital description of atoms.

Molecular Orbital Theory - A description of bonding that combines atomic orbitals from each bondedatom to produce a set of molecular orbitals.

Molecule - A chemical species containing a covalent bond.

Valence Shell Electron Pair Repulsion Theory - A theory used to predict bonding geometries that states that electron pairs will be distributed about the central atom to minimize electron pair repulsions

Deducing with Sociological Imagination

Sociology is the scientific study of human groups and social behavior. Sociologists focus primarily on human interactions, including how social relationships influence people's attitudes and how societies form and change. Sociology, therefore, is a discipline of broad scope: Virtually no topic—gender, race, religion, politics, education, health care, drug abuse, pornography, group behavior, conformity—is taboo for sociological examination and interpretation.

Sociologists typically focus their studies on how people and society influence other people, because external, or social, forces shape most personal experiences. These social forces exist in the form of interpersonal relationships among family and friends, as well as among the people encountered in academic, religious, political, economic, and other types of social institutions. In 1959, sociologist C. Wright Mills defined sociological imagination as the ability to see the impact of social forces on individuals' private and public lives. Sociological imagination, then, plays a central role in the sociological perspective.

As an example, consider a depressed individual. You may reasonably assume that a person becomes depressed when something “bad” has happened in his or her life. But you cannot so easily explain depression in all cases. How do you account for depressed people who have not experienced an unpleasant or negative event?

Sociologists look at events from a holistic, or multidimensional, perspective. Using sociological imagination, they examine both personal and social forces when explaining any phenomenon. Another version of this holistic model is the biopsychosocial perspective, which attributes complex sociological phenomena to interacting biological (internal), psychological (internal), and social (external) forces. In the case of depression, chemical imbalances in the brain (biological), negative attitudes (psychological), and an impoverished home environment (social) can all contribute to the problem. The reductionist perspective, which “reduces” complex sociological phenomena to a single “simple” cause, stands in contrast to the holistic perspective. A reductionist may claim that you can treat all cases of depression with medication because all depression comes from chemical imbalances in the brain.

On a topic related to depression, French sociologist Emile Durkheim studied suicide in the late 19th century. Being interested in the differences in rates of suicide across assorted peoples and countries and groups, Durkheim found that social rather than personal influences primarily caused these rates. To explain these differences in rates of suicide, Durkheim examined social integration, or the degree to which people connect to a social group. Interestingly, he found that when social integration is either deficient or excessive, suicide rates tend to be higher. For example, he found that divorced people are more likely to experience poor social integration, and thus are more likely to commit suicide than are married people. As another example, in the past, Hindu widows traditionally committed ritualistic suicide (called “suttee” meaning “good women”) because the cultural pressure at the time to kill themselves overwhelmed them.

Social forces are powerful, and social groups are more than simply the sum of their parts. Social groups have characteristics that come about only when individuals interact. So the sociological perspective and the social imagination help sociologists to explain these social forces and characteristics, as well as to apply their findings to everyday life.

Measuring the Economy

Macroeconomists use a variety of different observational means in their effort to study and explain how the economy as a whole functions and changes over time. One such method relies on personal experience. It is relatively simple to notice that your company is producing more than it has in the past or that a paycheck does not go as far as it used to. Yet while personal observations do provide information about the economy, that information can often be localized rather than universal, and may not accurately reflect the state of the economy as a whole.

In order to move beyond the limitations inherent in personal experiences, macroeconomists begin by systematically measuring the basic elements of the economy in order to derive standard and comprehensive statistics. This data provides information about the entire economy rather than simply about a single household or firm. Two of the most fundamental elements macroeconomists study are the total output of an economy (GDP) and the cost of living within an economy (CPI). Gross domestic product, or GDP, is an indicator of economic performance that measures the market value of goods and services produced within a country. This measurement is of great importance to consumers since it also equals the total income within an economy. The consumer price index, or CPI, is a cost of living indicator; it measures the total cost of goods and services purchased by a typical consumer within a country. This index allows economists and consumers to see just how much purchasing power a dollar yields, and to compare that power between different years and eras. Together, GDP and CPI show how much income exists within an economy and how much this income can purchase.

The concepts of GDP and CPI open the door to a scientific understanding of the functioning of the economy on a large, or macro, level. These are the most basic tools of measurement used by macroeconomists, policy makers, and consumers to understand and describe the economy. In fact, GDP and CPI are published and discussed regularly in the media. Through understanding the concepts of GDP and CPI, the world of macroeconomics begins to unfold...