Organic Chemistry

I want to share this article about organic chemistry. I think it would be so helpful for who is study chemisty.

Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation (by synthesis or by other means) of carbon-based compounds, hydrocarbons, and their derivatives. These compounds may contain any number of other elements, including hydrogen, nitrogen, oxygen, the halogens as well as phosphorus, silicon, and sulfur.
Organic compounds are structurally diverse. The range of application of organic compounds is enormous. They either form the basis of, or are important constituents of, many products including plastics, drugs, petrochemicals, food, explosives, and paints. They form the basis of almost all earthly life processes (with very few exceptions).

History

Friedrich Wöhler

Before the nineteenth century, chemists generally believed that compounds obtained from living organisms were too complex to be synthesized. According to the concept of vitalism, organic matter was endowed with a "vital force". They named these compounds "organic" and directed their investigations toward inorganic materials that seemed more easily studied.

During the first half of the nineteenth century, scientists realized that organic compounds can be synthesized in the laboratory. Around 1816 Michel Chevreul started a study of soaps made from various fats and alkalis. He separated the different acids that, in combination with the alkali, produced the soap. Since these were all individual compounds, he demonstrated that it was possible to make a chemical change in various fats (which traditionally come from organic sources), producing new compounds, without "vital force". In 1828 Friedrich Wöhler produced the organic chemical urea (carbamide), a constituent of urine, from the inorganic ammonium cyanate NH₄CNO, in what is now called the Wöhler synthesis. Although Wöhler was always cautious about claiming that he had disproved the theory of vital force, this event has often been thought of as a turning point.

In 1856 William Henry Perkin, while trying to manufacture quinine, accidentally manufactured the organic dye now known as Perkin's mauve.Through its great financial success, this discovery greatly increased interest in organic chemistry.
The crucial breakthrough for organic chemistry was the concept of chemical structure, developed independently and simultaneously by Friedrich August Kekulé and Archibald Scott Couper in 1858.Both men suggested that tetravalent carbon atoms could link to each other to form a carbon lattice, and that the detailed patterns of atomic bonding could be discerned by skillful interpretations of appropriate chemical reactions.
The history of organic chemistry continued with the discovery of petroleum and its separation into fractions according to boiling ranges. The conversion of different compound types or individual compounds by various chemical processes created the petroleum chemistry leading to the birth of the petrochemical industry, which successfully manufactured artificial rubbers, the various organic adhesives, the property-modifying petroleum additives, and plastics.
The pharmaceutical industry began in the last decade of the 19th century when the manufacturing of acetylsalicylic acid (more commonly referred to as aspirin) in Germany was started by Bayer.The first time a drug was systematically improved was with arsphenamine (Salvarsan). Though numerous derivatives of the dangerous toxic atoxyl were examined by Paul Ehrlich and his group, the compound with best effectiveness and toxicity characteristics was selected for production.
Although early examples of organic reactions and applications were often serendipitous, the latter half of the 19th century witnessed highly systematic studies of organic compounds.Beginning in the 20th century, progress of organic chemistry allowed the synthesis of highly complex molecules via multistep procedures.Concurrently, polymers and enzymes were understood to be large organic molecules, and petroleum was shown to be of biological origin. The process of finding new synthesis routes for a given compound is called total synthesis. Total synthesis of complex natural compounds started with urea, and increased in complexity to glucose and terpineol. In 1907, total synthesis was commercialized for the first time by Gustaf Komppa with camphor. Pharmaceutical benefits have been substantial. For example, cholesterol-related compounds have opened ways to synthesis complex human hormones and their modified derivatives. Since the start of the 20th century, complexity of total syntheses has been increasing, with examples such as lysergic acid and vitamin B12.
Biochemistry has only started in the 20th century, opening up a new chapter of organic chemistry with enormous scope. Biochemistry, like organic chemistry, primarily focuses on compounds containing carbon.

Characterization

Since organic compounds often exist as mixtures, a variety of techniques have also been developed to assess purity, especially important being chromatography techniques such as HPLC and gas chromatography. Traditional methods of separation include distillation, crystallization, and solvent extraction.
Organic compounds were traditionally characterized by a variety of chemical tests, called "wet methods", but such tests have been largely displaced by spectroscopic or other computer-intensive methods of analysis.Listed in approximate order of utility, the chief analytical methods are:

• Nuclear magnetic resonance (NMR) spectroscopy is the most commonly used technique, often permitting complete assignment of atom connectivity and even stereochemistry using correlation spectroscopy. The principal constituent atoms of organic chemistry - hydrogen and carbon - exist naturally with NMR-responsive isotopes, respectively ¹H and ¹³C.
• Elemental analysis: A destructive method used to determine the elemental composition of a molecule. See also mass spectrometry, below.
• Mass spectrometry indicates the molecular weight of a compound and, from the fragmentation patterns, its structure. High resolution mass spectrometry can usually identify the exact formula of a compound and is used in lieu of elemental analysis. In former times, mass spectrometry was restricted to neutral molecules exhibiting some volatility, but advanced ionization techniques allow one to obtain the "mass spec" of virtually any organic compound.
• Crystallography is an unambiguous method for determining molecular geometry, the proviso being that single crystals of the material must be available and the crystal must be representative of the sample. Highly automated software allows a structure to be determined within hours of obtaining a suitable crystal.

Traditional spectroscopic methods such as infrared spectroscopy, optical rotation, UV/VIS spectroscopy provide relatively nonspecific structural information but remain in use for specific classes of compounds.

Properties

Physical properties of organic compounds typically of interest include both quantitative and qualitative features. Quantitative information includes melting point, boiling point, and index of refraction. Qualitative properties include odor, consistency, solubility, and color.

Melting and boiling properties

In contrast to many inorganic materials, organic compounds typically melt and many boil. In earlier times, the melting point (m.p.) and boiling point (b.p.) provided crucial information on the purity and identity of organic compounds. The melting and boiling points correlate with the polarity of the molecules and their molecular weight. Some organic compounds, especially symmetrical ones, sublime, that is they evaporate without melting. A well known example of a sublimable organic compound is para-dichlorobenzene, the odiferous constituent of modern mothballs. Organic compounds are usually not very stable at temperatures above 300 °C, although some exceptions exist.

Solubility

Neutral organic compounds tend to be hydrophobic, that is they are less soluble in water than in organic solvents. Exceptions include organic compounds that contain ionizable groups as well as low molecular weight alcohols, amines, and carboxylic acids where hydrogen bonding occurs. Organic compounds tend to dissolve in organic solvents. Solvents can be either pure substances like ether or ethyl alcohol, or mixtures, such as the paraffinic solvents such as the various petroleum ethers and white spirits, or the range of pure or mixed aromatic solvents obtained from petroleum or tar fractions by physical separation or by chemical conversion. Solubility in the different solvents depends upon the solvent type and on the functional groups if present.

Solid state properties

Various specialized properties of molecular crystals and organic polymers with conjugated systems are of interest depending on applications, e.g. thermo-mechanical and electro-mechanical such as piezoelectricity, electrical conductivity (see conductive polymers and organic semiconductors), and electro-optical (e.g. non-linear optics) properties. For historical reasons, such properties are mainly the subjects of the areas of polymer science and materials science.

Nomenclature

Various names and depictions for one organic compound.‎

The names of organic compounds are either systematic, following logically from a set of rules, or nonsystematic, following various traditions. Systematic nomenclature is stipulated by specifications from IUPAC. Systematic nomenclature starts with the name for a parent structure within the molecule of interest. This parent name is then modified by prefixes, suffixes, and numbers to unambiguously convey the structure. Given that millions of organic compounds are known, rigorous use of systematic names can be cumbersome. Thus, IUPAC recommendations are more closely followed for simple compounds, but not complex molecules. To use the systematic naming, one must know the structures and names of the parent structures. Parent structures include unsubstituted hydrocarbons, heterocycles, and monofunctionalized derivatives thereof.
Nonsystematic nomenclature is simpler and unambiguous, at least to organic chemists. Nonsystematic names do not indicate the structure of the compound. Nonsystematic names are common for complex molecules, which includes most natural products. Thus, the informally named lysergic acid diethylamide is systematically named (6aR,9R)-N,N-diethyl-7-methyl-4,6,6a,7,8,9-hexahydroindolo-[4,3-fg] quinoline-9-carboxamide.
With the increased use of computing, other naming methods have evolved that are intended to be interpreted by machines. Two popular formats are SMILES and InChI.

Structural drawings

Organic molecules are described more commonly by drawings or structural formulas, combinations of drawings and chemical symbols. The line-angle formula is simple and unambiguous. In this system, the endpoints and intersections of each line represent one carbon, and hydrogen atoms can either be notated explicitly or assumed to be present as implied by tetravalent carbon. The depiction of organic compounds with drawings is greatly simplified by the fact that carbon in almost all organic compounds has four bonds, oxygen two, hydrogen one, and nitrogen three.

Classification of organic compounds

Functional groups

The family of carboxylic acids contains a carboxyl (-COOH) functional group. Acetic acid is an example.

The concept of functional groups is central in organic chemistry, both as a means to classify structures and for predicting properties. A functional group is a molecular module, and the reactivity of that functional group is assumed, within limits, to be the same in a variety of molecules. Functional groups can have decisive influence on the chemical and physical properties of organic compounds. Molecules are classified on the basis of their functional groups. Alcohols, for example, all have the subunit C-O-H. All alcohols tend to be somewhat hydrophilic, usually form esters, and usually can be converted to the corresponding halides. Most functional groups feature heteroatoms (atoms other than C and H). Organic compounds are classified according to functional groups, alcohols, carboxylic acids, amines, etc.

Aliphatic compounds

The aliphatic hydrocarbons are subdivided into three groups of homologous series according to their state of saturation:

• paraffins, which are alkanes without any double or triple bonds,
• olefins or alkenes which contain one or more double bonds, i.e. di-olefins (dienes) or poly-olefins.
• alkynes, which have one or more triple bonds.

The rest of the group is classed according to the functional groups present. Such compounds can be "straight-chain", branched-chain or cyclic. The degree of branching affects characteristics, such as the octane number or cetane number in petroleum chemistry.
Both saturated (alicyclic) compounds and unsaturated compounds exist as cyclic derivatives. The most stable rings contain five or six carbon atoms, but large rings (macrocycles) and smaller rings are common. The smallest cycloalkane family is the three-membered cyclopropane ((CH₂)₃). Saturated cyclic compounds contain single bonds only, whereas aromatic rings have an alternating (or conjugated) double bond. Cycloalkanes do not contain multiple bonds, whereas the cycloalkenes and the cycloalkynes do.

Aromatic compounds

Benzene is one of the best-known aromatic compounds as it is one of the simplest and most stable aromatics.

Aromatic hydrocarbons contain conjugated double bonds. The most important example is benzene, the structure of which was formulated by Kekulé who first proposed the delocalization or resonance principle for explaining its structure. For "conventional" cyclic compounds, aromaticity is conferred by the presence of 4n + 2 delocalized pi electrons, where n is an integer. Particular instability (antiaromaticity) is conferred by the presence of 4n conjugated pi electrons.

Heterocyclic compounds

The characteristics of the cyclic hydrocarbons are again altered if heteroatoms are present, which can exist as either substituents attached externally to the ring (exocyclic) or as a member of the ring itself (endocyclic). In the case of the latter, the ring is termed a heterocycle. Pyridine and furan are examples of aromatic heterocycles while piperidine and tetrahydrofuran are the corresponding alicyclic heterocycles. The heteroatom of heterocyclic molecules is generally oxygen, sulfur, or nitrogen, with the latter being particularly common in biochemical systems.
Examples of groups among the heterocyclics are the aniline dyes, the great majority of the compounds discussed in biochemistry such as alkaloids, many compounds related to vitamins, steroids, nucleic acids (e.g. DNA, RNA) and also numerous medicines. Heterocyclics with relatively simple structures are pyrrole (5-membered) and indole (6-membered carbon ring).
Rings can fuse with other rings on an edge to give polycyclic compounds. The purine nucleoside bases are notable polycyclic aromatic heterocycles. Rings can also fuse on a "corner" such that one atom (almost always carbon) has two bonds going to one ring and two to another. Such compounds are termed spiro and are important in a number of natural products.

Polymers

This swimming board is made of polystyrene, an example of a polymer.

One important property of carbon is that it readily forms chains, or networks, that are linked by carbon-carbon (carbon to carbon) bonds. The linking process is called polymerization, while the chains, or networks, are called polymers. The source compound is a called monomer.
Two main groups of polymers exist: synthetic polymers and biopolymers. Synthetic polymers are artificially manufactured, and are commonly referred to as industrial polymers. Biopolymers occur within a respectfully natural environment, or without human intervention.
Since the invention of the first synthetic polymer product, bakelite, synthetic polymer products have frequently been invented.
Common synthetic organic polymers are polyethylene (polythene), polypropylene, nylon, teflon (PTFE), polystyrene, polyesters, polymethylmethacrylate (called perspex and plexiglas), and polyvinylchloride (PVC).

Both synthetic and natural rubber are polymers.

Varieties of each synthetic polymer product may exist, for purposes of a specific use. Changing the conditions of polymerization alters the chemical composition of the product and its properties. These alterations include the chain length, or branching, or the tacticity.
With a single monomer as a start, the product is a homopolymer.

Secondary component(s) may be added to create a heteropolymer (co-polymer) and the degree of clustering of the different components can also be controlled.

Physical characteristics, such as hardness, density, mechanical or tensile strength, abrasion resistance, heat resistance, transparency, colour, etc. will depend on the final composition.

Biomolecules

Maitotoxin, a complex organic biological toxin.

Biomolecular chemistry is a major category within organic chemistry which is frequently studied by biochemists. Many complex multi-functional group molecules are important in living organisms. Some are long-chain biopolymers, and these include peptides, DNA, RNA and the polysaccharides such as starches in animals and celluloses in plants. The other main classes are amino acids (monomer building blocks of peptides and proteins), carbohydrates (which includes the polysaccharides), the nucleic acids (which include DNA and RNA as polymers), and the lipids. In addition, animal biochemistry contains many small molecule intermediates which assist in energy production through the Krebs cycle, and produces isoprene, the most common hydrocarbon in animals. Isoprenes in animals form the important steroid structural (cholesterol) and steroid hormone compounds; and in plants form terpenes, terpenoids, some alkaloids, and a unique set of hydrocarbons called biopolymer polyisoprenoids present in latex sap, which is the basis for making rubber.

Small molecules

In pharmacology, an important group of organic compounds is small molecules, also referred to as 'small organic compounds'. In this context, a small molecule is a small organic compound that is biologically active, but is not a polymer. In practice, small molecules have a molar mass less than approximately 1000 g/mol.

Molecular models of caffeine.

Fullerenes

Fullerenes and carbon nanotubes, carbon compounds with spheroidal and tubular structures, have stimulated much research into the related field of materials science.

Others

Organic compounds containing bonds of carbon to nitrogen, oxygen and the halogens are not normally grouped separately. Others are sometimes put into major groups within organic chemistry and discussed under titles such as organosulfur chemistry, organometallic chemistry, organophosphorus chemistry and organosilicon chemistry.

Organic synthesis

A synthesis designed by E.J. Corey for oseltamivir (Tamiflu). This synthesis has 11 distinct reactions.

Synthetic organic chemistry is an applied science as it borders engineering, the "design, analysis, and/or construction of works for practical purposes". Organic synthesis of a novel compound is a problem solving task, where a synthesis is designed for a target molecule by selecting optimal reactions from optimal starting materials. Complex compounds can have tens of reaction steps that sequentially build the desired molecule. The synthesis proceeds by utilizing the reactivity of the functional groups in the molecule. For example, a carbonyl compound can be used as a nucleophile by converting it into an enolate, or as an electrophile; the combination of the two is called the aldol reaction. Designing practically useful syntheses always requires conducting the actual synthesis in the laboratory. The scientific practice of creating novel synthetic routes for complex molecules is called total synthesis.
There are several strategies to design a synthesis. The modern method of retrosynthesis, developed by E.J. Corey, starts with the target molecule and splices it to pieces according to known reactions. The pieces, or the proposed precursors, receive the same treatment, until available and ideally inexpensive starting materials are reached. Then, the retrosynthesis is written in the opposite direction to give the synthesis. A "synthetic tree" can be constructed, because each compound and also each precursor has multiple syntheses.

Organic reactions

Organic reactions are chemical reactions involving organic compounds. While pure hydrocarbons undergo certain limited classes of reactions, many more reactions which organic compounds undergo are largely determined by functional groups. The general theory of these reactions involves careful analysis of such properties as the electron affinity of key atoms, bond strengths and steric hindrance. These issues can determine the relative stability of short-lived reactive intermediates, which usually directly determine the path of the reaction.
The basic reaction types are: addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions and redox reactions. An example of a common reaction is a substitution reaction written as:

Nu⁻ + C-X → C-Nu + X⁻

where X is some functional group and Nu is a nucleophile.
The number of possible organic reactions is basically infinite. However, certain general patterns are observed that can be used to describe many common or useful reactions. Each reaction has a stepwise reaction mechanism that explains how it happens in sequence—although the detailed description of steps is not always clear from a list of reactants alone.
The stepwise course of any given reaction mechanism can be represented using arrow pushing techniques in which curved arrows are used to track the movement of electrons as starting materials transition through intermediates to final products.

Top Ten Reasons You Should Quit Facebook

 

Top Ten Reasons You Should Quit Facebook

Facebook privacy policies keep going down the drain. That's enough reason for many to abandon it. Here you will find nine more:

After some reflection, I've decided to delete my account on Facebook. I'd like to encourage you to do the same. This is part altruism and part selfish. The altruism part is that I think Facebook, as a company, is unethical. The selfish part is that I'd like my own social network to migrate away from Facebook so that I'm not missing anything. In any event, here's my "Top Ten" reasons for why you should join me and many others and delete your account.

10. Facebook's Terms Of Service are completely one-sided

Let's start with the basics. Facebook's Terms Of Service state that not only do they own your data (section 2.1), but if you don't keep it up to date and accurate (section 4.6), they can terminate your account (section 14). You could argue that the terms are just protecting Facebook's interests, and are not in practice enforced, but in the context of their other activities, this defense is pretty weak. As you'll see, there's no reason to give them the benefit of the doubt. Essentially, they see their customers as unpaid employees for crowd-sourcing ad-targeting data.

9. Facebook's CEO has a documented history of unethical behavior

From the very beginning of Facebook's existence, there are questions about Zuckerberg's ethics. According to BusinessInsider.com, he used Facebook user data to guess email passwords and read personal email in order to discredit his rivals. These allegations, albeit unproven and somewhat dated, nonetheless raise troubling questions about the ethics of the CEO of the world's largest social network. They're particularly compelling given that Facebook chose to fork over $65M to settle a related lawsuit alleging that Zuckerberg had actually stolen the idea for Facebook.

8. Facebook has flat out declared war on privacy

Founder and CEO of Facebook, in defense of Facebook's privacy changes last January: "People have really gotten comfortable not only sharing more information and different kinds, but more openly and with more people. That social norm is just something that has evolved over time." More recently, in introducing the Open Graph API: "... the default is now social." Essentially, this means Facebook not only wants to know everything about you, and own that data, but to make it available to everybody. Which would not, by itself, necessarily be unethical, except that ...

7. Facebook is pulling a classic bait-and-switch

At the same time that they're telling developers how to access your data with new APIs, they are relatively quiet about explaining the implications of that to members. What this amounts to is a bait-and-switch. Facebook gets you to share information that you might not otherwise share, and then they make it publicly available. Since they are in the business of monetizing information about you for advertising purposes, this amounts to tricking their users into giving advertisers information about themselves. This is why Facebook is so much worse than Twitter in this regard: Twitter has made only the simplest (and thus, more credible) privacy claims and their customers know up front that all their tweets are public. It's also why the FTC is getting involved, and people are suing them (and winning).
Check out this excellent timeline from the EFF documenting the changes to Facebook's privacy policy.

6. Facebook is a bully

When Pete Warden demonstrated just how this bait-and-switch works (by crawling all the data that Facebook's privacy settings changes had inadvertently made public) they sued him. Keep in mind, this happened just before they announced the Open Graph API and stated that the "default is now social." So why sue an independent software developer and fledgling entrepreneur for making data publicly available when you're actually already planning to do that yourself? Their real agenda is pretty clear: they don't want their membership to know how much data is really available. It's one thing to talk to developers about how great all this sharing is going to be; quite another to actually see what that means in the form of files anyone can download and load into MatLab.

5. Even your private data is shared with applications

At this point, all your data is shared with applications that you install. Which means now you're not only trusting Facebook, but the application developers, too, many of whom are too small to worry much about keeping your data secure. And some of whom might be even more ethically challenged than Facebook. In practice, what this means is that all your data - all of it - must be effectively considered public, unless you simply never use any Facebook applications at all. Coupled with the OpenGraph API, you are no longer trusting Facebook, but the Facebook ecosystem.

4. Facebook is not technically competent enough to be trusted

Even if we weren't talking about ethical issues here, I can't trust Facebook's technical competence to make sure my data isn't hijacked. For example, their recent introduction of their "Like" button makes it rather easy for spammers to gain access to my feed and spam my social network. Or how about this gem for harvesting profile data? These are just the latest of a series of Keystone Kops mistakes, such as accidentally making users' profiles completely public, or the cross-site scripting hole that took them over two weeks to fix. They either don't care too much about your privacy or don't really have very good engineers, or perhaps both.

3. Facebook makes it incredibly difficult to truly delete your account

It's one thing to make data public or even mislead users about doing so; but where I really draw the line is that, once you decide you've had enough, it's pretty tricky to really delete your account. They make no promises about deleting your data and every application you've used may keep it as well. On top of that, account deletion is incredibly (and intentionally) confusing. When you go to your account settings, you're given an option to deactivate your account, which turns out not to be the same thing as deleting it. Deactivating means you can still be tagged in photos and be spammed by Facebook (you actually have to opt out of getting emails as part of the deactivation, an incredibly easy detail to overlook, since you think you're deleting your account). Finally, the moment you log back in, you're back like nothing ever happened! In fact, it's really not much different from not logging in for awhile. To actually delete your account, you have to find a link buried in the on-line help (by "buried" I mean it takes five clicks to get there). Or you can just click here. Basically, Facebook is trying to trick their users into allowing them to keep their data even after they've "deleted" their account.

2. Facebook doesn't (really) support the Open Web

The so-called Open Graph API is named so as to disguise its fundamentally closed nature. It's bad enough that the idea here is that we all pitch in and make it easier than ever to help Facebook collect more data about you. It's bad enough that most consumers will have no idea that this data is basically public. It's bad enough that they claim to own this data and are aiming to be the one source for accessing it. But then they are disingenuous enough to call it "open," when, in fact, it is completely proprietary to Facebook. You can't use this feature unless you're on Facebook. A truly open implementation would work with whichever social network we prefer, and it would look something like OpenLike. Similarly, they implement just enough of OpenID to claim they support it, while aggressively promoting a proprietary alternative, Facebook Connect.

1. The Facebook application itself sucks

Between the farms and the mafia wars and the "top news" (which always guesses wrong - is that configurable somehow?) and the myriad privacy settings and the annoying ads (with all that data about me, the best they can apparently do is promote dating sites, because, uh, I'm single) and the thousands upon thousands of crappy applications, Facebook is almost completely useless to me at this point. Yes, I could probably customize it better, but the navigation is ridiculous, so I don't bother. (And, yet, somehow, I can't even change colors or apply themes or do anything to make my page look personalized.) Let's not even get into how slowly your feed page loads. Basically, at this point, Facebook is more annoying than anything else.
Facebook is clearly determined to add every feature of every competing social network in an attempt to take over the Web (this is a never-ending quest that goes back to AOL and those damn CDs that were practically falling out of the sky). While Twitter isn't the most usable thing in the world, at least they've tried to stay focused and aren't trying to be everything to everyone.
I often hear people talking about Facebook as though they were some sort of monopoly or public trust. Well, they aren't. They owe us nothing. They can do whatever they want, within the bounds of the laws. (And keep in mind, even those criteria are pretty murky when it comes to social networking.) But that doesn't mean we have to actually put up with them. Furthermore, their long-term success is by no means guaranteed - have we all forgotten MySpace? Oh, right, we have. Regardless of the hype, the fact remains that Sergei Brin or Bill Gates or Warren Buffett could personally acquire a majority stake in Facebook without even straining their bank account. And Facebook's revenue remains more or less a rounding error for more established tech companies.
Click to viewWhile social networking is a fun new application category enjoying remarkable growth, Facebook isn't the only game in town. I don't like their application nor how they do business and so I've made my choice to use other providers. And so can you.
Dan Yoder

That's what Dan Yoder thinks. I don't like facebook, either. But i think what have been written is exaggerated. Facebook can be useful, in right hands. And it's valid in every internet page. I enjoy using Facebook, even it can be dangerous. :P