What are strong nucleophiles?  

Strong nucleophiles:

Strong nucleophiles…this is why molecules react. The nucleophilic site of the nucleophile is the region of a molecule that is reactive and has the electron density.

Strong nucleophiles are VERY important throughout organic chemistry, but will be especially important when trying to determine the products of elimination and substitution (SN1 vs SN2) reactions.  In fact, there is not a more important part of an organic chemistry reaction than the nucleophile and the electrophile.   So, let’s look at what makes strong nucleophiles:

There are generally three factors to remember when discussing how nucleophilic a reactant is:

1)      Size – Generally (but not always) the more linear and/or smaller the nucleophile, the more nucleophilic it will be.  This is because it can react at more sites and will not be sterically hindered if it is smaller or linear.  Remember, smaller nucleophiles can fit into more places, therefore will be able to react at more places and will necessarily be more nucleophilic.  This has a lot to do with sterics. You will hear a lot about bulky bases, which are nucleophilic but too darn big to be a nucleophile and can only be a base.

2)       Electronegativity– The more electronegative an atom is, the less nucleophilic it will be.   This is because more electronegative atoms will hold electron density closer, and therefore will be less likely to let that electron density participate in a reaction.  We see this in calculations and experiments that show nucleophilicity decreases as you get closer to fluorine on the periodic table (C > N > O > F).

3)      Polarizability– The more polarizable an atom is, the more nucleophilic it will be.   Polarizability is defined as the ability to distort the electron cloud of an atom, which allows it interact with a reaction site more easily.  Generally, polarizability increases as you travel down a column of the periodic table (I > Br > Cl > F)

Below is a table of relative nucleophilic strength.  This is relative because nucleophilic strength is also dependent on other factors in the reaction, such as solvent. I am not a huge fam of memorizing charts, but this might be a good one to know pretty well.

As shown above, as a general rule, the anion of a reactant will be a better nucleophile than the neutral form.  (i.e. RCO₂^– is a better nucleophile than RCO₂H)

But nucleophiles are also bases?

Think about it for a second….good nucleophiles (as shown above) can have a negative charge and will almost always have a lone pair. Bases accept protons, with a negative charge or lone pair. [gasp] So it makes sense there will be at least some overlap between bases and nucleophiles. This is a major consideration when looking at SN vs E reactions.

Here are a couple of good rules to remember:

1. Bases will not be good nucleophiles if they are really bulky or hindered. A variety of amine bases can be bulky and non-nucleophilic.

2. Nucleophiles will not be good bases if they are highly polarizable. I- is the best example of this. Great nucleophile, really poor base.

Why do we care about strong nucleophiles?

Organic chemistry is all about reactions. We really need to know what is nucleophilic and what is not so that we can determine what is going to react at the electrophilic site. If you know this, you can predict the products of organic chemistry reactions, even ones that you have not seen before.

The next step is to learn about electrophiles. 

Please visit our recent post on this topic –> Electrophilic addition. Not to humble brag, but it is pretty good.

For more information on this and other topics of organic chemistry interest, please visit organic chemistry

Reference: Nucleophilic strength

The post Strong nucleophiles you need to know [with study guide & chart] appeared first on Organic Chemistry Made Easy by AceOrganicChem.

As to properly reference the authors, here is a guide from Lynchburg College on how to write a science report well.

A Few General Characteristics of Good Writing in Chemistry

1.  Clear.  This is perhaps the most important characteristic of all writing, but is especially important when detailed, complicated experimental data is discussed.  Be sure you say what you mean and mean what you say.   Use short sentences and get to the point.

2.  Dispassionate.  Good scientific writing is free of bias and personal opinion.  Report the facts.

3.  Mechanically sound.  This goes without saying.  If your writing is free of grammatical and spelling errors, it is easier for the reader to understand.

4.  Documented.  Statements and conclusions are supported by data, not feelings or opinions.  If your data are inconclusive, it is better to state this than to force the data to fit some hypothesis or literature value.

Other hints and suggestions for written work in chemistry:

• Do not use first person (“I,” “we,” etc.). Use the past tense (you did the experiment already).
• Do not be verbose.  Get to the point!
• Do not start a sentence with a number unless it is part of a chemical name.
• Do not capitalize the names of chemicals unless you are beginning a sentence.
• Do not use the words or phrases “basically,” “dealt with,” “dealing with,” “create(d).” Leave bases to baseball and solutions with pH > 7; leave dealing to Las Vegas and Atlantic City; and leave creating to the Fine Arts department.
• Regardless of  what your spell-checker says, “absorbency” is not a word unless we are analyzing diapers.  Always use “absorbance.”
• Do not say things like “the goal of this experiment was to introduce to the student the technique of chromatography.”  Say “Carotenoids were purified using chromatography.” Leave the student out of the discussion.  Everyone knows you are a student. Tell the reader what you DID and HOW you did it.
• Use the words “precise” and “accurate” correctly.  Accuracy refers to how close your value is to the standard or known value.  Precision refers to how close together your results are; data cannot be precise unless you have done more than one trial.
• Use the words “clear” and “colorless” correctly.  Water is clear and colorless.  Sunglasses are clear and green.  Milk is cloudy and colorless (white).  Muddy water is cloudy and brown.

• Report data and results with units and with the appropriate number of significant figures.
• Do not include statements of opinion.  For example, stating that the experiment was difficult or tedious is your opinion and does not belong in a reporting of the results of your study.
• The literature value of a physical property is just that; it is not the “literary” value.
• Use numbered endnotes for referencing.  You need to reference anything you have to look up, even if it is in your textbook, the lab manual, or the CRC handbook or Aldrich catalog.
• Please run the spell-checker.
• Please staple together the pages of your reports.

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What is resonance?

What is resonance (in organic chemistry) in 2022? In one sentence, it is the concept where electrons (bonds) are delocalized over three or more atoms which cannot be depicted with one simple Lewis structure.

Resonance is one of those issues that you will have to deal with for both semester I & II of organic chemistry.  It is much better to have a solid understanding of it now, rather than have to worry about it later.  The basic goal of resonance structures is to show that molecules can move electrons and charges onto different atoms on the molecule.  Resonance generally makes a molecule more stable because the charge (or bond) is now delocalized and not “forced” onto an atom that might not want it.  More on this is discussed below!

What is the resonance effect and why care?

The best way to discuss this concept is to talk about the resonance effect. This concept says that the more resonance structures you that can be formed means more stability in that molecular compound. Said another way: a carbocation structure with no resonance structures will be less stable than one with multiple resonance structures.

Sometimes, molecules can be represented with more than one Lewis/resonance structure, where the only difference is the location of pi electrons. Electrons in sigma bonds have a fixed location; these are called localized and never move. Conversely,  pi electrons are referred to as delocalized, because they can be easily moved around.  Together, these Lewis diagrams are then known as resonance structures or resonance contributors or resonance canonicals. The actual molecule has characteristics of each of the parts, and can represented as a resonance hybrid (which you can think of as a cross-breed).  Resonance hybrids are a more accurate way to think about resonance structures, because it is more like what the structure looks like in nature. 

Some Rules of Resonance

Below are some handy rules of resonance.  If you learn these and think about them when tackling different problems, you will be able to handle whatever is thrown at you.

1) Know each atom’s “natural state”. We talk about this in a different post on atoms’ natural state. You need to recognize what each atom we deal with generally looks like, in an uncharged state.  This will help you to construct the Lewis Dot structure on which you will base your structures.  Remember that halogens and hydrogens are always terminal, meaning that are at the end of the molecule and only have one bond, and therefore, they will not (generally) participate.

2) Atom positions will not change.  Once you have determined that an atom is bonded to another atom, that order will not change in a resonance structure.  If they do change, it is no longer a resonance structure, but is now a constitutional isomer or a tautomer.  Here is a nice post on constitutional isomers to check out. This is important and instructors will try to trick you on it. Don’t fall for it.

3) Check the structure you have created to make sure that it follows the octet rule.  This will become much easier once you have a better handle on the “natural state” of atoms.  If you violate the octet rule, you need to go back and check to make sure you didn’t make a mistake.  Don’t remember the octet rule?  It is where each atom needs to have eight electrons in its outer most shell to be most stable.  This is important to go back and review if you don’t remember it. Here is a good post on it.

4) When two or more structures can be drawn, the one with the fewest total charges is the most stable.  In the example below, A is more stable than B.  Multiple charges on atoms CAN exist (such as a zwitterion), but this is usually seen when there is an acid and a base on the same molecule, not in this case. Once you see more organic chemistry, this will just become intuitive to you.

5) When two or more  structures can be drawn, the more stable has the negative charge on the more electronegative atom.  Hopefully, this makes sense to you. The more electronegative atom is better able to accommodate a negative charge, therefore the more stable structure will put the negative charge on the atom in which it will be more stable. In the example below, A is more stable than B.

6) In the end, each resonance structure should have the same overall charge and total number of electrons (bonds + lone pairs) as when you started.  If you started with a negative overall charge, you should end with one. If it does not, you most likely made a mistake somewhere.

7) Resonance affect the length of a bond between two atoms.  We have another post on this topic, which we called resonance part 2. This is far less intuitive but makes more sense when you think of it in terms of resonance hybrids. Basically, resonance can make two bond lengths equal even though we might draw it as something different on paper, like we show below here:

Take Home Message:  Resonance is like telemarketers.  They are never going to go away, so you need to learn them well.

Reference: resonance

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Structures of molecules can be difficult to piece together at first when you are just starting in an organic chemistry class. Hopefully you retained some of this knowledge from general chemistry. If not, one of the tricks that can greatly help with this is to know the uncharged or “normal” state for atoms that are commonly found in organic molecules.   Here is a table of the most common of those:

      – C has four bonds and no lone pairs

       – N has three bonds and one lone pair

       – Halogens (F, Cl, Br, I) have one bond and three lone pairs. 

       – O has two bonds and two lone pairs

       – H has one bond and no lone pairs

Three more rules:

–          C, N, O are central atoms, meaning that they will always be in the middle of your molecule.

–          H and halogens are terminal atoms, meaning that they will only have one bond and be at the ends of molecules.

–          With the exception of H, atoms in group I & group II are only counterions (+1 or +2 and not involved in resonance).

Remember, these rules are for when the atom is uncharged; this does not apply to charged atoms.  For example, a carbocation (a positively charged carbon atom) will have only three bonds with no lone pairs while a carbanion (a negatively charged carbon atom) wlll have three bonds with one lone pair, and a carbene will have two bonds with two lone pairs.

Notice that all of these carbons still follow the octet rule.  However, beware of atoms that do not follow the octet rule, as phosphorus is an example of an atom that can have more than an octet of electrons.  Shown below is triphenylphosphine oxide, a byproduct of the Wittig reaction.

Elements with open d-subshells, like phosphorous and sulfur, do not always follow the octet rule.  More examples of this are SF₆ and PCl₅.  However, carbon, nitrogen and oxygen will follow the octet rule.

The post Know the “normal” state for common organic atoms [3 rules to live by] appeared first on Organic Chemistry Made Easy by AceOrganicChem.

Epoxidation of Alkenes

Somewhere in one of your exams, you will see at least one question on epoxidation of alkenes. Quick tip: Before you start on alkenes, make sure you are good with alkanes, specifically the naming alkanes.

The reaction:  What is epoxidation? An epoxide is a 3-membered ring containing two carbon atoms and one oxygen atom. Many students like to remember it as a cyclic ether. It is interesting because it is easily opened due to small ring strain and due to the electronegativity of the oxygen atom.

The reagents and starting materials:

1) What is an alkene?  An alkene is an unsaturated hydrocarbon containing at least one double bond. They are ubiquitous (i love snooty words) in organic chemistry. The double bond itself has two parts, a sigma bond which holds the atoms together and a pi bond which strengthens in overall bond through added electron density, making them electron rich.

2) What is epoxidation of an alkene? The epoxidation reaction is where an alkene is subjected to a peroxyacid to convert it into an epoxide. Another way to say it is epoxidation is the electrophilic addition of oxygen to the double bond of the alkene.

3) What reagents can you use to create the epoxide? Generally, peroxy acids are used in this electrophilic addition to the alkene. A peroxy acid is like a carboxylic acid, but has two oxygen atoms bonded to each other.

There are several types of commonly used peroxyacid such as proxy trifluoroacetic acid, peroxyacetic acid, hydrogen peroxide, and mCPBA, which is the most common of all. It is a peroxyacid and is shown below:

HOWEVER, there is another reagent, OsO₄ , which also can give epoxides, but will give the opposite stereochemistry. More on that below.

The mechanism: The mechanism for the reaction is relatively complex and may (or may not) be something your professors want you to know about, but hell, it’s good practice.   While it is considered a single step reaction, it involves several changes. The double bond is our nucleophile and attacks the more electrophilic oxygen. This breaks the weak oxygen-oxygen bond and creates a new carbonyl. Once this carbonyl is formed, rearrangement occurs and the more electrophilic oxygen is released to become the oxygen of the epoxide.

The stereochemistry: The stereochemistry associated with this reaction is interesting and important. As the reaction can occur on a cis or trans alkene, we see the two different products come from these two different starting materials. The oxygen can only attack from one face of the alkene. This means that the stereochemistry of the alkene is retained. Translation: if you start with a cis alkene you will get a cis epoxide. If you start with a trans alkene, you will get a trans epoxide.

Further, remember that if you start with a di or tri-substituted alkene, you very well may create new stereocenters. However, if you remember the golden rule of chirality, you will know that  you need to start with chirality in order to finish with it. These alkenes are not chiral to start with, therefore we will end with a racemic mixture. If there is some chirality in the molecule, somewhere near the double bond then that chirality can influence which face the peroxyacid is attacked from, but will not exclusively give a chirally pure product.

The reaction the reaction is versatile, and works on many different alkenes. Please remember that the reaction will not work on the double bonds of an aromatic compound.

The alternative reaction uses OsO₄ . Since Osmium tetroxide is toxic and costs a ton of money it is not the preferred reactant for these kinds of epoxidation reactions. Catalytic osmium tetroxide  and stoichiometric amounts of a decent oxidizing agent (such as H2O2) are used to make it less dangerous. Although syn diols will result from the reaction of KMnO₄ and an alkene, potassium permanganate is less useful since it gives poor yields of the product because of overoxidation. For this reason, we have focused on the peroxy acids in this article, however, please remember that on your exam, OsO₄ is a good reagent to obtain syn diols.

Some peroxy acid examples:

What can you do with epoxides once you have it? Great question! Epoxides, because they are so strained, are easily opened and can form other products. The first one that comes to mind is that epoxides can be opened up into trans-diols. It is a simple reaction, but highly useful, and usually the way you need to make a trans-diol on one of your exams.

We rate the importance of this reaction, the epoxidation of alkenes, as four beakers out of five. This means you should know epoxidation reaction and the products you can get from it, but maybe don’t need to know the ins and outs of the mechanism for it. BE SURE to ask your prof though!

Reference: NIH epoxidation in the human body

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WARNING: Solvent-Separated Ion Pair concept is somewhat advanced. It can be simply explained by your professor might not require you to have knowledge of it. Only moderate to severe organic chemistry nerds should proceed.

Hi everybody, just wanted to give out a quick tip when looking at SN1 reactions.  Many students believe that SN1 reactions give totally racemic products, but this is not actually the case.  The amount of loss of chirality depends on the leaving group, the solvent and the nucleophile.

We all know that the SN1 reaction proceeds through a carbocation intermediate, which cannot hold the stereochemistry that the carbon atom previously possessed.  (In other words, if you start with a chiral carbon and go through a cation, you will have a trigonal, achiral cation) . Shown below is a very simple example of an SN1 reaction between t-butyl chloride and sodium cyanide.

 However your starting material does not actually have the same chance of being attacked by the cyanide from either side.  Many times, the leaving group can come back to the cation on the same side.  This partially blocks one face of the cation.  The net result is that your carbocation CANNOT be equally attacked from both sides.  Below is a stages that the leaving group can go through as it takes off.

In this example, our starting material (which will become the electrophile in the SN1 reaction) is t-butyl chloride. The far left structure is the starting material with a normal covalent bond. In the middle is the contact ion pair, which is also called the intimate ion pair. This is an ionic bond, which the chlorine is a full anion, but has not gone far from the carbocation. In the contact ion pair, the solvent has not come between the two charges and the chloride ion has the highest likelihood of blocking nucleophile attack from that side. At any time, the chloride ion can re-attach to the carbocation and become a covalent bond, as shown by the double arrows. From a contact ion pair the chlorine can get farther from the carbocation and become a solvent-separated ion pair. Here the chloride ion still has some affect on which face the nucleophile attacks from, but less influence than if it is was a contact ion pair.

When the nucleophile attacks, it can come in from either face of carbocation, but not in equal ratios, as the chlorine is still blocking one face slightly more than the other.  While the preference for the unblocked face may be small, you can see the difference in some reactions. This means that the SN1 reaction will lose some (or a lot of) chirality, but will not usually become totally racemic.

 Good luck on those exams and happy reacting.

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The Alkane Formula

Before we can answer the question of what is the alkane formula, we have to ask ourselves what is an alkane. An alkane is a simple hydrocarbon containing carbon and hydrogen single bonded to each other, with a carbon backbone. Any molecule with this structure is going to have the formula C_nH_n+2, where n is any integer. Let’s look at some examples of this:

Please note, that this formula doesn’t tell us anything about the structure of the alkane, it only tells us that is fully unsaturated. For example, both pentane and 2,2-dimethylpropane will both be fully unsaturated and have the same molecular formula, but completely different structures and physical properties therefore we have to be very careful not to make assumptions about the structure of an alkane just based on its formula.

It’s a nice trick to know that any time you see a molecule with the formula C_nH_n+2, you know it is a fully saturated hydrocarbon, meaning that there are no double or triple bonds only single bonds. The degree of unsaturation, or “some of double bonds and rings” (SODAR) can be expressed using a similar formula. Here is a great post discussing the SODAR formula.

A quick rule of thumb to be able to determine if a molecule is saturated or not is just to ask if there are more than double the number of hydrogens as compared to carbon in the molecule.  For example, if you have a hydrocarbon with the formula C₅H₁₂, we know that there are more than double the number of hydrogen therefore this is saturated. If we have a structure with the formula C₅H₁₀, there are only double the number of hydrogens therefore this is unsaturated at some point in the molecule. What this little rule of thumb doesn’t tell us is where that unsaturation is or what type of unsaturation it is, a double bond or a ring.

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The steps of free radical reactions in 2022

This is one of the best depictions of the steps of free radical reactions I have seen.   It shows what can go on in this reactions and how we get from starting material to desired final product.

Radical reactions: a quick overview first. A radical reaction is a reaction which occurs by a free radical mechanism (duh) and results in the substitution of one or more of the atoms or groups present in the substrate by different atoms or groups. Homolysis is the process by which one makes two new radicals by breaking a covalent bond, leaving each of the fragments with one of the electrons in the bond. Because breaking a chemical bond requires energy, homolysis occurs under the addition of heat or light.

Initiation = One neutral provides two radicals.  

This is what starts the entire reaction.  This is also the only initiation step that can occur, as CH₄ is not going to break off an H*. Remember that we need light or heat or some sort of radical initiator to start the initiation step in a radical reaction.

Propagation = 1 neutral + 1 radical provides a different neutral and a different radical.  

In this reaction, the most likely propagation is chlorine abstracting a proton from methane to give HCl and the methyl radical.  The next step is where the methyl radical breaks up two Cl atoms.  What I really like about this depiction is that it shows that the Cl* from reaction 3 can be recycled back into step 2.  This means that the reaction is self-propagating.  This also means that IN THEORY you could have one initiation reaction, followed by a bunch of different propagations, ending with one termination reaction.  Of course, in real life, for many reasons, this does not happen as there are lots of differnt initiation reactions.

Termination = 2 radicals providing one neutral.

 The part to remember here is that any two radicals can get together to terminate the reaction and form a neutral species.  Since we have 2 types of radicals in the reaction (Cl* and CH₃*) , there are three combinations of potential termination steps.  Reaction 4 gives us back starting material, so it is fine.  Reaction 6 gives us product, so it is also fine.  Reaction 5 give us a byproduct, which strangely enough can replace methane in the propagation step and give us another by-product.

Think about this picture and figure out all of the side reactions that might occur to fowl up the reaction.  Then, (for you advanced students) think about what ways exist that you can minimize those side reactions.

Here is the quick summary of radical reactions:

1. Initiation = 1 neutral provides two radicals.
2. Propagation = 1 neutral + 1 radical provides a different neutral and a different radical.
3. Termination = 2 radicals providing one neutral.

Hope this was helpful to you all, and as always, happy reacting.

The post Steps of a Free Radical Reactions [simplified – with a great diagram] appeared first on Organic Chemistry Made Easy by AceOrganicChem.

What is a hydrogen bond?

A hydrogen bond is an electrostatic attraction between an electronegative atom (one that has lone pair electrons) and a hydrogen atom bound to an electronegative atom.

Because the electronegative atom has lone pair electrons and steals some electron density from other places, it takes on a partial negative charge, symbolized by d-.  Conversely, the hydrogen atom bound to that electronegative atom has some of its electrons drawn away, making it partially positive, or d+.  When two of these molecules interact in solution, the d+ from hydrogen is attracted to the d- of the electronegative atom and a hydrogen bond is formed.

In contrast to a covalent bond, where two atoms formally share the two electrons in the bond, the two electrons of the hydrogen bond completely reside on the electronegative atom and are only attracted to the hydrogen atom. This makes a hydrogen bond much weaker than a covalent bond.  Symbolically, we show a hydrogen bond as a dashed or dotted line, instead of a full line, to remind the user that it is not a formal bond.

So, how strong is a hydrogen bond?

The answer is not very.  Remember, this is not a “bond” in the traditional sense, it is an electrostatic attraction.  The hydrogen bond has only 5% or so of the strength of a covalent bond. However, when many hydrogen bonds can form between two molecules (or parts of the same molecule), the resulting union can be sufficiently strong as to be quite stable. The length of the hydrogen bond varies slightly, depending on what the electronegative atom is.  In water, the length is generally accepted to be 1.98A.

One of the best examples of the hydrogen bonding is water.  Oxygen is the electronegative atom here and provides the electrons for the hydrogen bond from one of its two lone pairs. One of the two hydrogen atoms on water will obviously be the electron acceptor.  This means that each water molecule can have up to four hydrogen bonds at any one time, with two bonds to each lone pair and two bonds to each hydrogen atom.

Moreover, hydrogen bonding is quite dynamic, meaning that hydrogen bonds are constantly changing.  In water, that means that they are constantly breaking and forming between the different water molecules. The pictures above are just snapshots in time, because the process of forming and breaking bonds happens way to fast to see or measure.

But it occurs in other places too.   Now that we know hydrogen bonding occurs in water, it is not that great a stretch to think that it would also occur in alcohols.  Moreover, hydrogen bonding occurs in amines, carbonyls, and other organic chemistry and biological molecules.  Below is a representation of the hydrogen bonding that might occur between water and ammonia.  Notice that hydrogen can bond with nitrogen (once) or oxygen (twice).

Why do we care about such a weak little bond?

• Hydrogen bonding affects the physical properties of molecules, such as BP. Hydrogen bonding tends to increase boiling point, when compared to molecules of a similar size that don’t hydrogen bond.
• Hydrogen bonding makes liquids into better solvents.  This is because it can adhere to solutes better through this bonding….who would have thought?
• Hydrogen bonding affects conformations, such as in enols. This one is pretty cool. Generally, if a molecule can be in either conformation, it will choose the keto form because it is more stable.  However, if there is a highly-stabilizing hydrogen bond, it might be more stable in the enol form.

• Hydrogen bonding greatly affects our biology. Numerous examples in biochemistry show how important hydrogen bonding is. In DNA, hydrogen bonds between nitrogenous bases in nucleotides on the two strands of (guanine pairs with cytosine, adenine with thymine) give rise to the double-helix structure that is crucial to the transmission of genetic information.  In proteins, protein folding is reliant on hydrogen bonding. Receptor-substrate binding cannot generally occur without hydrogen bonding.  Further, as stated above, it keeps water as a liquid at much lower temperatures than one would predict based on the size/weight of the molecule. We clearly couldn’t live without hydrogen bonds.

Reference: Hydrogen bonds

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Functional Groups in Organic Chemistry

Welcome back.  Let’s not beat around the bush on this one: functional groups in organic chemistry are why we can do any organic chemistry in the first place. Functional groups are the basis of why molecules can and will react with each other. Without functional groups, everything would be straight chain alkanes and other boring hydrocarbons. So it’s important to learn functional groups, and how they will interact with nucleophiles and electrophiles to react to form new organic molecules.

Major Disclaimer:  This is not meant to be a comprehensive review of all of the functional groups out there, however it’ll be a nice start and a good reference for you.

Hopefully you understand why they are important, now we just have to determine what some of the different types are.

What to learn about nucleophiles?  Click on the link to check it out

Hydrocarbons: these are simply composed of carbon and hydrogen. This group is alkanes, cycloalkanes, alkenes, and alkynes.  Don’t forget about conjugated alkenes too, as they are important in many organic processes such as the Diels-Alder reaction.  While alkanes and cycloalkanes are not particularly reactive, alkenes and alkynes definitely are.

Carbonyls: a “carbon double bond oxygen” is a carbonyl.  It is one of the more important electrophiles you will see in this course.  While there are different variations which can make the carbonyl more or less reactive, the basic functional group is still the same.  The important point here is to know which types of carbonyls are more electrophilic and which ones are less. Generally speaking, if there is an electron withdrawing group attached to the carbonyl carbon, that carbonyl will be more electrophilic and more reactive.

Alkyl Halides: alkanes which are connected to a halogen atom (F, Cl, I, and Br) are good electrophiles.  These can participate in nucleophilic substitution reactions and elimination reactions.  They reactivity depends on the type of alkyl halide (F, Cl, I, Br), its substitution (primary, secondary, tertiary) and the desired reaction (SN1, SN2, E1, E2).

Alcohols, Amines, and Thiols: these are generally very good nucleophiles, as the heteroatoms have lone pairs which will attack an electrophile.

Ethers: do not undergo many organic reactions themselves, but sometimes can be the product of a reaction.  Some chemists refer to ethers as “dead molecules” because of their low reactivity.

And now for some crazy functional groups….

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