organic-chemistry

"Constitutional isomerism is not limited to alkanes—it occurs widely throughout organic chemistry. Constitutional isomers may have different carbon skeletons (as in isobutane and butane), different functional groups (as in ethanol and dimethyl ether), or different locations of a functional group along the chain (as in isopropylamine and propylamine). Regardless of the reason for the isomerism, constitutional isomers are always different compounds with different properties but with the same formula."

"In earlier times, when relatively few pure organic chemicals were known, new compounds were named at the whim of their discoverer … As the science of organic chemistry slowly grew in the 19th century, so too did the number of known compounds and the need for a systematic method of naming them. … A chemical name typically has four parts in the IUPAC system of nomenclature: prefix, parent, locant, and suffix. The prefix identifies the various substituent groups in the molecule, the parent selects a main part of the molecule and tells how many carbon atoms are in that part, the locants give the positions of the functional groups and substituents, and the suffix identifies the primary functional group. … For historical reasons, some of the simpler branched-chain alkyl groups also have nonsystematic, common names, as noted earlier."

"When chemists make chiral compounds—molecules that behave like object and mirror image, such as amino acids, sugars, drugs, or nucleic acids—they like to use asymmetric catalysis, in which a chiral catalyst selectively accelerates the reaction that leads to one mirror-image isomer, also called enantiomer."

"If we were to isolate each enantiomer in pure form, we would find that we could not distinguish between them on the basis of their physical properties, such as boiling points, melting points, and densities. This result should not surprise us: Their bonds are identical and so are their energy contents. However, when a special kind of light, called plane-polarized light, is passed through a sample of one of the enantiomers, the plane of polarization of the incoming light is rotatedin one direction (either clockwise or counterclockwise). When the same experiment is repeated with the other enantiomer, the plane of the polarized light is rotated by exactly the same amount but in the opposite direction."

"In contrast with enantiomers, diastereomers, because they are not mirror images of each other, are molecules with different physical and chemical properties."

"Organometallic chemists try to understand how organic molecules or groups interact with compounds of the inorganic elements, chiefly metals. These elements can be divided into the main group, consisting of the s and p blocks of the periodic table, and the transition elements of the d and f blocks."

"Molecules that are not identical to their mirror images are kinds of stereoisomers called enantiomers (Greek enantio, meaning “opposite”). Enantiomers are related to each other as a right hand is related to a left hand and result whenever a tetrahedral carbon is bonded to four different substituents (one need not be H)."

"During the first half of this century most syntheses were developed by selecting an appropriate starting material, after a trial and error search for commercially available compounds having a structural resemblance to the target of synthesis. Suitable reactions were then sought for elaboration of the chosen starting material to the desired product. Synthetic planning in most instances was strongly dependent on an assumed starting point. In the fall of 1957 I came upon a simple idea which led to an entirely different way of designing a chemical synthesis. In this approach the target structure is subjected to a deconstruction process which corresponds to the reverse of a synthetic reaction, so as to convert that target structure to simpler pecursor structures, without any assumptions with regard to starting materials. Each of the precursors so generated is then examined in the same way, and the process is repeated until simple or commercially available structures result. This “retrosynthetic” or “antithetic” procedure constitutes the basis of a general logic of synthetic planning which was developed and demonstrated in practice over the ensuing decade."

"The construction of a synthetic tree by working backward from the target molecule (TM) is called retrosynthetic analysis or antithesis. The symbol ⇒ signifies a reverse synthetic step and is called a transform. The main transforms are disconnections, or cleavage of C-C bonds, and functional group interconversions (FGI). Retrosynthetic analysis involves the disassembly of a TM into available starting materials by sequential disconnections and functional group interconversions. Structural changes in the retrosynthetic direction should lead to substrates that are more readily available than the TM. Synthons are fragments resulting from disconnection of carbon-carbon bonds of the TM. The actual substrates used for the forward synthesis are the synthetic equivalents (SE). Also, reagents derived from inverting the polarity (IP) of synthons may serve as SEs."

"Heterolytic retrosynthetic disconnection of a carbon-carbon bond in a molecule breaks the TM into an acceptor synthon, a carbocation, and a donor synthon, a carbanion. In a fomal sense, the reverse reaction – the formation of a C-C bond – then involves the union of an electrophilic acceptor synthon and a nucleophilic donor synthon."

"Computer programs are available that suggest possible disconnections and retrosynthetic pathway. Such programs utilize the type of systematic analysis outlined above to identify key bonds for disconnection and plausible functional group inter-conversions."

"Metals, particularly lithium and magnesium, act on haloalkanes to generate new compounds, called organometallic reagents, in which a carbon atom of an organic group is bound to a metal. These species are strong bases and good nucleophiles and as such are extremely useful in organic syntheses."

"Note carefully the difference between enantiomers and diastereomers: enantiomers have opposite configurations at all chirality centers, whereas diastereomers have opposite configurations at some (one or more) chirality centers but the same configuration at others."

"The emergence of organic chemistry as a scientific discipline heralded a new era in human development. Applications of organic chemistry contributed significantly to satisfying the basic needs for food, clothing and shelter. While expanding our ability to cope with our basic needs remained an important goal, we could, for the first time, wony about the quality of life. Indeed, there appears to be an excellent correlation between investment in research and applications of organic chemistry and the standard of living."

"Typically, the goal of synthesis is to construct complex organic chemicals from simpler, more readily available ones. To be able to convert one molecule into another, chemists must know organic reactions."

"Why is an entire branch of chemistry devoted to the study of carbon-containing compounds? We study organic chemistry because just about all of the molecules that make life –possible proteins, enzymes, vitamins, lipids, carbohydrates, and nucleic acids–contain carbon."

"The modern definition of organic chemistry is the chemistry of carbon compounds. What is so special about carbon that a whole branch of chemistry is devoted to its compounds? Unlike most other elements, carbon forms strong bonds to other carbon atoms and to a wide variety of other elements. Chains and rings of carbon atoms can be built up to form an endless variety of molecules. It is this diversity of carbon compounds that provides the basis for life on Earth. Living creatures are composed largely of complex organic compounds that serve structural, chemical, or genetic functions."

"Chemistry touches everyone's daily life, whether as a source of important drugs, polymers, detergents, or insecticides. Since the field of organic chemistry is intimately involved with the synthesis of these compounds, there is a strong incentive to invest large resources in synthesis. Our ability to predict the usefulness of new organic compounds before they are prepared is still rudimentary. Hence, both in academia and at many chemical companies, research directed toward the discovery of new types of organic compounds continues at an unabated pace. Also, natural products, with their enormous diversity in molecular structure and their possible medicinal use, have been and still are the object of intensive investigations by synthetic organic chemists."

"In a way, the “learning” and “using” of organic chemistry is much like learning and using a language. You need the vocabulary (i.e., the reactions) to be able to use the right words, but you also need the grammar (i.e., the mechanisms) to be able to converse intelligently. Neither one on its own gives complete knowledge and understanding, but together they form a powerful means of communication, rationalization, and predictive analysis. To highlight the interplay between reaction and mechanism, icons are displayed in the margin at appropriate places throughout the text."

"Introductory courses in organic chemistry usually rely primarily on the valence bond description of molecular structure. Valence bond theory was the first structural theory applied to the empirical information about organic chemistry. During the second half of the nineteenth century, correct structural formulas were deduced for a wide variety of organic compounds. The concept of “valence” was recognized. That is, carbon almost always formed four bonds, nitrogen three, oxygen two, and the halogens one."

"The central message of chemistry is that the properties of a substance come from its structure. What is less obvious, but very powerful, is the corollary. Someone with training in chemistry can look at the structure of a substance and tell you a lot about its properties. Organic chemistry has always been, and continues to be, the branch of chemistry that best connects structure with properties."

"No organic chemist, however brilliant, understands the detailed chemical working of the human mind or body very well."

"Part of the charm of synthetic organic chemistry derives from the vastness of the intellectual landscape along several dimensions. First, there is the almost infinite variety and number of possible target structures that lurk in the darkness waiting to be made. Then, there is the vast body of organic reactions that serve to transform one substance into another, now so large in number as to be beyond credibility to a non-chemist. There is the staggering range of reagents, reaction conditions, catalysts, elements, and techniques that must be mobilized in order to tame these reactions for synthetic purposes. Finally, it seems that new information is being added to that landscape at a rate that exceeds the ability of a normal person to keep up with it. In such a troubled setting any author, or group of authors, must be regarded as heroic if through their efforts, the task of the synthetic chemist is eased."

"To my delight, I discovered that fascinating combination of rigor/hypothesis, hard-core theory/intuition, and commercial-level practicality/artistic elegance known as organic chemistry in a 1954 course at Yeshiva University. It was already clear that one of the challenges of Orgo (particularly for the pre-meds) would be the systemization of a huge body of factual data, allowing for retrieval of critical information at critical times (exams, etc)."

"Since the numbers of functional groups are relatively small, it is possible to classify a very large number of individual compounds by a relatively small number of functional groups. So the first step to enlightenment in organic chemistry is to realize the key role that functional groups play in simplifying the subject, and the second step is to learn the functional groups by name, structure, and formula."

"What is organic chemistry, and why should you study it? The answers to these questions are all around you. Every living organism is made of organic chemicals. … Anyone with a curiosity about life and living things, and anyone who wants to be a part of the remarkable advances now occurring in medicine and the biological sciences, must first understand organic chemistry."

"The present data collection is intended to serve as an aid in the interpretation of molecular spectra for the elucidation and confirmation of the structure of organic compounds. It consists of reference data, spectra, and empirical correlations from 1H, 13C, 19F, and 31P nuclear magnetic resonance (NMR), infrared (IR), mass, and ultraviolet–visible (UV/Vis) spectroscopy. It is to be viewed as a supplement to textbooks and specific reference works dealing with these spectroscopic techniques. The use of this book to interpret spectra only requires the knowledge of basic principles of the techniques, but its content is structured in a way that it will serve as a reference book also to specialists."

"An organic chemist is primarily concerned with (a) the synthesis of organic molecules of particular interest to the pharmaceutical and agrochemical industries and (b) the way these molecules interact in biological pathways."

"It may seem odd that a whole discipline is devoted to the study of a single element in the periodic table, when more than 100 elements exist. It turns out, though, that there are far more organic compounds than any other type. Organic chemicals affect virtually every facet of our lives, and for this reason, it is important and useful to know something about them."

"The goal, as in previous editions is to give equal weight to the three fundamental aspects of the study of organic chemistry: reactions, mechanisms, and structure. A student who has completed a course based on this book should be able to approach the literature directly, with a sound knowledge of modern organic chemistry."

"Organic chemistry is the chemistry of compounds that contain the element carbon. … carbon compounds are central to the structure of living organisms and therefore to the existence of life on Earth. We exist because of carbon compounds."