Could you explain why we would want to attempt to remove an impurity of a water insoluble thiol from a water insoluble alcohol by washing with aqueous NaOH? (Thiols are more acidic than alcohols, so can be significantly deprotonated in an aqueous solution at pKa 14 or less. - GS).

^^^So would the same answer apply if the question was to attempt to remove an impurity of a water insoluble alcohol from a water insoluble ester? (No. pKa of alcohols are about 15. - GS).

What is the overall synthetic outcome of hydroboration of alkenes, followed by oxidation?” I know hydroboration is against Markovnikov’s rule.  Is the answer addition of water against markovnikov’s rule (Yes. - GS) or addition of boron in the syn-fashion against the Markovnikov’s rule? (No, because it is followed by oxidation. - GS).

^^^^^^Just out of curiousity what would the product be if this reaction (addition of water against the markovnikov's rule) took place assuming that the alkene was like ethene? (Ethanol, but for this example, the rule does not apply because both carbons have same number of hydrogens. - GS).

In general I was wondering is there a “clue” that allows you to tell whether the reaction is first order or second order, (Usually it is same as the number of particles interacting on the rate-limiting step. - GS). I can easily differentiate between E and S reactions and can also tell when its SN1 or Sn2 when the reaction is written out even if only partially written out but I sm still struggling with which is which “verbally”?  (The best illustration is given by U.CAN. - GS).

Is more branched more stable? (For the alkane chain - usually yes. - GS).

A good leaving group is a weak base correct? (Yes. - GS).

”Polymerization of which compound will produce a polymer with the following structure?” What is the answer and how did you get that? (Take out the repeating polymer chain fragment and complete the free valencies with double bonds. - GS).

How can you rotate around a pi bond in a butane molecule? (No, there is no such bond. - GS). I thought all bonds in butane are sigma? (Correct. - GS).

Surface of potential energy is given by heat effect, number of steps, reaction rates for all steps

Balanced chemical equation is given by molecular coefficients for all reactants and products

Curved arrrow. .  .  redistribution of electrons and charges between the nuclei

Is this correct? (Yes. - GS).

For those struggling with formal charge, this video is very helpful. https://www.khanacademy.org/science/organic-chemistry/organic-structures/formal-charge-resonance/v/formal-charge-i  (Very good video. Formal charges are also connected to molecular geometry. However, students who attended my lectures will find it redundant. - GS).

Dr. Sereda, is Br the only element that can exceed it’s octect? (No. Any element of period 3 and higher can do it. - GS). Carbon and oxygen cannot? (Correct. They are in period 2 - GS).

Dr. Sereda, how do you know if a compound contains only primary hydrogens? (It happens when the compound has only primary carbons that bonded to hydrogens. - GS).

Is 2,2-dimethylpropane a compound that only has primary hydrogens? (Yes. - GS).

Is trans generally more stable than cis? (Yes, for linear hydrocarbons - for sure. - GS).

Does the fact that a molcule is a primary, seconadary, tertiary,etc carbon really matter if it is given that the octet is complete for the carbon? (“Primary” etc refers to carbons, not molecules. - GS). Wouldnt the formal charge always just be zero for carbon if the octet is complete? (No. It is zero when carbon forms 4 covalent bonds and in some other cases, such as free radical and carbene. - GS).

Different strength of attraction between molecules of alkanes makes possible to separate petroleum into heating gas by distillation correct? (Yes, because of different boiling points. - GS).

Is staggered more stable than eclipse conformation? (Yes, for alkanes. - GS).

Is it correct that a chiral center must have four different substituents attached? (Yes, counting hydrogen. - GS).

Staggered configuration is more stable than eclipsed correct? (Yes for alkanes because of the prevalence of steric repulsion. For other types of compounds, it depends on the individual intramolecular interactions. - GS).

How are heterocyclic amines (HCAs) form from cooking and how do we avoid this cancer-causing, adduct-forming agents? Giving up steak is NOT an option. (It is a series of aldol condensations, dehydrations, oxidations, and cyclizations, which can be minimized by steam cooking or pressure cooking with antioxidant herbs. The art is to maintain temperature high enough to give you a yummy crust, but too low to induce the above listed reactions. High pressure of water vapor also keeps dehydrations under control. The carcinogenic polycyclic aromatic compounds are especially easily formed from steroid hormones that could be given to the animal to accelerate its growth, or could be produced by the animal’s body when it is under stress and abused. Nature has its ways for fighting back. - GS).

Can you explain the difference between stereoisomers and constitutional isomers? (In constitutional isomers, atoms are connected in a different order. In stereoisomers, atoms are connected in the same order, but are placed at different locations. - GS).

Dr. Sereda, is the formula for cycloalkanes CnH2n? (Yes, and also for alkenes. - GS). Consequently, is the formula for alkanes CnH2n+2? (Yes. - GS).

What makes something a chiral center vs. an achiral center? (A chiral center must have all four attached groups different. - GS).

I’m having trouble understanding the difference between constitutional isomers and identical isomers. Could you explain this? (There are no identical isomers. Isomers must be different compounds. - GS).

Can you go over the differences between ‘R’ and ‘S’ compounds? (There are no R- and S-compounds. This term refers to chiral centers. - GS). Do these only apply to enantiomers? (No. It applies to any chiral center. - GS).

So when the pH equals the pKa, in this case when the pH=9, then the amino groups would only be half protonated, correct? (Almost. Half of them will be fully protonated. - GS)

Is the hydrogen on the alpha carbon more acidic than the hydrogen on the OH group of the carboxylic acid?  (Their pKas are about 17 and 5 correspondingly. - GS.) What about if there are two carbonyl groups attached by an alpha carbon? (That pKa is about 9 - GS).

Acid donates H+, does conjugative acid accept H+? (No. Bronsted bases accept H+ - GS).

What was it you said in lecture about if the pKa>pH then that means. .  . ? I know on the blog you said pKa = pH, the concentrations of acid and conjugate base are equal, but does that mean that if the pKa>pH the concentration of the conjugate base is greater than the concentration of acid?  (No. Equilibrium favors the acid under those conditions. - GS).

I’m still having a little trouble in relating pKa to pH in terms of deprotonation. (If pKa = pH, the concentrations of acid and conjugate base are equal. - GS)

Dr. Sereda, what is the difference in the apparatus between a distillation and reflux? (In distillation, the distillate is taken out, in refluxing - it is dripping back. - GS).

Dr. Sereda, when we “wash” something in lab with a separatory funnel, is that an example of extraction? (Yes. - GS).

If you increase atmospheric pressure will it INCREASE or DECREASE the boiling point. (It will increase the boiling point, because it will require a higher temperature to raise the vapor pressure up to the atmospheric pressure. - GS).

Dr. Sereda, what are desirable characteristics of solvents for recrystallization (Higher solubility at higher temperatures and lower solubility at lower temperatures, non-reactivity with the compound, ease of removal, but other scenarios are possible. - GS). and extraction? (Higher solubility of the desired compound and lower solubility of non-desired compounds, immiscibility with the liquid you are extracting from, non-reactivity with the compound, ease of removal. - GS)

What type of reaction is shown for the synthesis of the alkenes? (4-methyl-2-pentanol +SOCl2→ 4-methyl-2-chloropentane and then add CH3CH2ONa and CH3CH2OH and heat → Alkenes) Does is proceed by an E2 mechanism because it is a secondary alcohol? (Yes, because alkoxide is a strong base. - GS).  Are there any hydride or alkyl shifts in this case?  (No, because there are no carbocations involved. - GS).

I looked up distribution coefficient on the internet but I am having some trouble understanding it for the liquid-liquid extraction. Do you have a simple definition? and then how do you calculate it? Then when you know K what does it mean to have a large K versus a small K? (The distribution coefficient is the ratio of concentrations of a compound in different phases. If it significantly differs from 1, than most of the compound went to one phase. If it is about 1, the concentrations are equal. The more different the distribution coefficients are for different compounds, the better the separation is. - GS).

Dr. Sereda, is the reaction between phenylmagnesium bromide and CO2 form a benzene ring bonded to a carbon(which is double bonded to oxygen), bonded to an O with a negative charge? (Yes. It produces a benzoate. - GS).

Dr. Sereda, would the reaction between phenylmagnesium bromide and H2o form a benzene ring with a hydrogen coming out?(Yes. It will be just benzene itself. - GS).

So I don’t need to draw the hydrogen coming out of the ring? (No. It is implied by the valency of carbon. - GS).

Just making sure: when a carboxylic acid and an amine react without heat and without a catalyst the product is an ammonium salt but when a carboxylic acid and an amine react with either heat or with a catalyst the product is an amide? (You are correct. - GS).

What are the conditions for acyl substitution? (It depends on the nucleophile and the leaving group. - GS). When will it produce a carboxylic acid derivative versus a salt? (Salt is also considered a carboxylic acid derivative and is produced under alkaline hydrolysis, that is with OH- as the nucleophile. - GS).

Hi Dr. Sereda I was curious how does the boiling behavior of a pure liquid differ from that of a solution? Thanks!! (Both cases obey the same rule - they start to boil when the total vapor pressure becomes equal atmospheric pressure. However, as opposed to a pure liquid, for a mixture, compositions of the vapor and the liquid are different, so as you are distilling out some vapor, composition of the liquid is changing - GS).

How do you know if something can be hydrolyzed to become a carboxylic acid or its salt? For example, how do you know the “derivatives” have this ability and what does the reaction look like? (A carbon must have three bonds (in any combination of single, double, and triple bonds) to atoms with at least one lone electron pair. - GS).

Will a Claisen condensation proceed under both acidic and basic conditions? (No, only under basic conditions, and only if that base is an alkoxide. Some other bases are possible, but rare. - GS).

What makes something a carboxylic acid derivative? (Ability to be hydrolyzed to a carboxylic acid or its salt. - GS).

Is there a difference between a reaction with “slight” heating vs. normal heating? Will it change anything? (Higher temperatures increase the reaction rate, decrease selectivity, favor enthropy-driven reactions, and may produce more gaseous compounds, which also plays to enthropy. - GS).

How do you know which carbon is the “alpha” carbon? (Next to the carbonyl group. - GS).

Dr. Sereda, I am having a hard time understanding how to identify lipids.  Could you possibly go over what makes a lipid tomorrow and how we identify them? (Lipids are natural compounds soluble in fats. - GS).

Dr. Sereda, what is the significance of “washing” something in lab? (Removing something ytou do not want or extracting something you want. - GS). For example, why do we wash some of our solutions with water and sodium bicarbonate? What does it do? (Either to remove an unwanted acid, or extract the desired compound to water as a carboxylate salt. - GS).

How does the alkaline hydrolysis work to produce a secondary amine? (Same way is for alkaline hydrolysis of esters, but with nitrogen instead of oxygen. See U.CAN - alkaline hydrolysis - GS).

Number four on last years quiz asks about why amides are much less basic than amines. I am under the assumption that this is due to resonance stabilization of amides. (You are correct. - GS).

Are amides much less basic, than amines because of their alkyl substituents at nitrogen? (No. Because of the carbonyl group withdrawing by conjugation the lone electron pair on nitrogen. - GS). Is that because of the resonance between them? (Yes. - GS).

Could you have a reaction between a carboxylic acid and an amine with a catalyst but without heating? (You need a reagent other than a catalyst, such as a carbodiimid derivative. - GS). Conversely, what about without a catalyst but with heating? Would these yield different answers if there is only one not both? (Either heat or a coupling reagent will produce an amide. - GS).

What is the product of a reaction between a carboxylic acid and an amine without heating, then? (Ammonium salt of carboxylic acid. - GS).

Dr. Sereda, what is the product of a reaction between a carboxylic acid and an amine with heating? Is it an amide? (Yes. - GS)

In general will a carboxylic acid + an alcohol with an acid catalyst result in the formation of an ester and water through Fischer Esterification? (Yes. The reverse reaction is called acid-catalysed hydrolysis of esters. - GS).

Is PCC’s job to turn alcohol into an aldehyde/ketone? (Yes. - GS).

Will acetal hydrolysis only happen under acidic conditions? (Yes. That is why non-reducing sugars can not open up to the reducing non-cyclic form. It is a very important question. - GS).

Is it any type of Sn1, E1, Sn2, E2, reaction? I thought you said something about that in class. (Conversion of hemiacetals to acetals (and the reverse reaction) is protonation followed by SN1 followed by deprotonation. - GS).

Is “Nucleophilic Addition to Carbonyl Group” an Sn1 reaction? (No. - GS).

What is supposed to happen to a enol when its in equilibrium with a ketone? (As a net result, hydrogen jumps between oxygen and carbon, end the double bond shifts from C=C to C=O. - GS).

Are hemiacetals very unstable and want to be acetals? (Usually yes, unless they are stabilized by cyclization. Example: alpha- and beta-glucose (and any other monosaccharide) are most favorable forms of glucose, and they are hemiacetals. They also tend to go back to the carbonyl compound and alcohol. - GS).

What are protecting groups (Removable groups stable under certain conditions. - GS) and why are acetals good ones? (They are stable in the presence of strong bases. - GS).

What exactly happens in a Friedel-Crafts Acylation? (Introduction of an acyl group into an aromatic ring by electrophilic substitution, catalyzed by a Lewis acid, most commonly AlCl3. - GS).

I recall you saying something about how in acidic conditions, something is deactivated, while something else is activated, and the opposite in basic. Would you mind stating this again? (Acids activate the carbonyl and deactivate the nucleophile by protonation. Bases may activate the nucleophile by deprotonation. - GS).

What is the PhC(O) benzoyl group and what is the significance? (It is a common part of many compounds such as acetophenone used in cosmetics, construction materials, and organic synthesis. It is also part of benzoic acid (conservant) and cocaine. That is just a few examples. - GS).

Dr. Sereda, what does “carb” meain in the name 2-methylcyclohexanecarbaldehyde? (It means that the aldehyde group contains a carbon, which is not a part of the principal chain. - GS).

(Here are 6 common pitfalls for chemical structure, bonding, and acids-bases: https://drive.google.com/file/d/0BxwgAv6oGg81aXM0WmxoYVU1WVk/view?usp=sharing   - GS).

I found this PDF about carbocations to be really helpful, if anyone else is interested!

http://www.chem.ucla.edu/harding/tutorials/cc.pdf (thank you!!)

-I’m not sure how many of you have heard of it, but I really enjoy KhanAcademy.org (Good job - GS).

Does a cyclopentane have double bonds anywhere on it? (No. - GS).

Dr. Sereda, would you mind posting on here what you said in class about how temperature and other factors affect reactions? (Higher temperature, stronger and more concentrated acid or base favor elimination, including dehydration on the last step of the aldol reaction. Generally speaking, higher temperature usually increases the reaction rate and favors entropy-driven equilibria. - GS).

In the formation of imines, is it always catalyzed by an acid? Or can the amine group attack as a nucleophile to the carbonyl carbon without the formation of a resonance stabilized carbonation? (Imines can form without acidic catalysis, but some other derivatives R-NH2 cannot. - GS).

Do ketones turn into enols? (Only if it has an alpha-hydrogen. - ) Is this reaction reversible?(Yes, as far as I know the reaction begins with a base, which puts a negative charge on the alpha carbon. When you then add acid, this would form an enol. The reaction will be reversible.-Anonymous rabbit) (Correct for both. - GS).

For formation of imine, enamine, hydrazone, are these in acidic conditions? (Each of those reactions has an optimal pH, depending on the substituent. - GS).

How do I tell the difference between an acetal and a hemiacetal by just looking at the structures. (Hemiacetals have an OH group, connected to the carbon, connected to oxygen. - GS).  All I understand is that hemiacetals are unstable and will go toward acetal formation  (Correct, only under acidic conditions. They will also go back to the carbonyl compound under any conditions. - GS).

I am not understanding the differences between an acid catalyzed aldol reaction (Enol plus activated carbonyl - GS). and a base catalyzed (Enolate plus non-activated carbonyl. - GS). aldol reaction.

Could you go over aldol reaction in class again? I just dont fully understand it. (OK. Briefly, it is just addition of an enol or enolate to an activated or non-activated carbonyl group, often followed by dehydration. - GS).

Does the formation of an acetal require alcohol and a proton? (Yes, and also an aldehyde or a ketone. - GS).

Could you go over aldol reaction in class again? I just dont fully understand it. (OK. Briefly, it is just addition of an enol or enolate to an activated or non-activated carbonyl group, often followed by dehydration. - GS).

I understand that the HCN adds to the aldehyde, so does this result in the formation of an alcohol? (Yes, which is also a nitrile. - GS).

What type of reaction is Cyanohydrin synthesis from (U.CAN)? (Nucleophilic addition to the carbonyl group. - GS).

What makes something an alpha position? (Next carbon. - GS).

Dr. Sereda, what does the prefix tert- mean? (Tertiary - GS).

Where does the “carb” come from for 2-methylcyclohexanecarbaldehyde? Is that just how you name it? (Yes, it is common for cyclic aldehydes.. - GS). Why is it different in the structure “3-methylbutanal”- is that not an aldehyde because it’s not cyclic? (Exactly. - GS).

When the pKa of a particular compounds is lower, does that mean it protonates more as opposed to if it were higher? (No, it is a stronger acid and tries to get rid of protons. - GS). Would it deprotonate at such higher pKas? (No - GS). Why is this?(Because at higher pH (it is a weaker acid and holds protons tighter. - GS).

How can a reactant mixture be made basic without adding a hydroxide salt? I know that if a salt contains an anion that reacts with water to produce hydroxide ions and also contains a cation that does not react with water then the resulting solution would be expected to be basic ... (Yes, this is one way. Another one is formation of hydroxide-anions in a redox-reaction. - GS).

Practical applications of organic chemistry in dentistry: https://drive.google.com/a/usd.edu/file/d/0BxwgAv6oGg81cDNlcGJ4RVpaNkk/view

U.CAN - Understand Curved Arrow Notation. Animation of organic reaction mechanisms:  http://ochem.orgfree.com/

Why does hydrogen bonding affect the boiling point? Yes I know this, but why? (It makes molecules stick to each other more and it takes more energy to separate them to the gas phase. Note: It does not apply to tertiary amines. - GS).

Dr. Sereda, in an acylation of amines, is it essentially a substitution reaction and the amine acts as a nucleophile? (Yes, it is an acyl substitution. The mechanism is similar to that shown in U.CAN for Fischer esterification. - GS). For instance, if an acyl group attached to a halide reacts with an amine group, des the halide act as a leaving group on the acyl group, and the amine attacks as a nucleophile (Yes. You are correct. - GS).

Dr. Sereda, amines with alkyl substituents increase in basicity up until the 3 substituent, why is that? (Due to better delocalization of the positive charge by substituents in the more substituted protonated form (ammonium). However, it works only for the gas phase. In solution, solvation kicks in, and things become more complicated. - GS).

Dr. Sereda, can you please go over acid/base strength of amines, specifically in benzene rings with multiple substituents? Thanks! (OK, Electron acceptors in the benzene ring, especially resonance acceptors in o- and p- positions further decrease basicity of amines. - GS).

When looking for a compound that is the most reactive with a nucleophile do you always choose the molecule that is the least electronegative?(No. Electronegativity refers to an atom rather than to a molecule. - GS) Would it be correct if I had said: the most reactive compound with a nucleophile is the molecule that contains  the least electronegative atom because this reaction will lead to the best leaving group? (No. Most electronegative atom makes the weakest base if you compare elements of the same period with the same charge. - GS).

Dr. Sereda, out of the choices A. I-, B. H2O, C. Cl-, D. CH3OH, and E. F-, which would be the LEAST reactive with bromoethane? (Choices B, D, and E are bad for the reaction. One of them can be made worse than another depending on solvent and concentration. Nucleophilicity of F- will benefit from an aprotic solvent, water and methanol - from using them as solvents. - GS).

Do inductie acceptors, resonance acceptors, resonance donors, hyperconjugative donors, and hyperconjugative acceptors all proceed preferentialyl to the meta-position? If not, which ones don’t and what do they proceed to? (You need to look at the existing substituent, not the incoming one. - GS).

For a compound to absorb UV-Light at the longest wavelength and highest intensity, would it always be in regards to the length of the conjugated chain; thus the longest chain of conjugation= the best compound to absorb UV-light at the longest wavelength and the highest intensity? (Yes, but for comparison, it must be a linear (non-cyclic) conjugation. For example, graphene has a huge number of conjugated benzene rings, but stays colorless. - GS).

Is sp hybridized, in general, less stable than say sp2 or sp3? I know that the sp has a shorter bond length than sp3 and that the bonds involved in sp are stronger than the sp3 but I am not 100% sure how that relates to stability. I was thinking that the single bonds are more stable because they have less energy in the bonds and thus sp3 will generally be more stable than sp, is that right? (I would not directly relate energy to the hybridization model, except for the orbital holding a lone electron pair. - GS).

I cant seem to remember what “poly” means? I know that the -diene means 2 double bonds, -ene means a single double bond; cis means on  the same side of a double whereas trans means across/opposite sides of the double bond. Thanks. (“Poly-” means “polymer”. - GS).

Hello Dr. Sereda, I have a quick question about multiple substituents on benzene rings. If you have two substituents that are donors, how you can tell which is the more activating donors group? (The resonance donor wins - GS). For instance, if you had a OH and a methyl group in the para positions to each other, (OH-group will determine orientation - GS).  how would you know where the incoming substituent would attach? (ortho-position with respect to the OH-group - GS).

How do you know when a substituent will hyperconjugate? How can you tell if it is a donor or an acceptor? (Hyperconjugation is essential for alkyl substituents (donors) and polyfluoroalkyl substituents (acceptors). For our substituents, hyperconjugation is usually muted by other effects and should not be considered. - GS).

How can you tell what a free radical is? (It is an orbital occupied by a single electron, which is denoted by a dot on organic structures.. - GS)

Can we go over why halogens are ortho, para-directing but a deactivating group again? (F is so electronegative that it overrides even the resonance donating effect of its lone electron pairs. For Cl, Br, and I, the lone electron pairs are taking too much space, which makes their overlap with the pi-system of the benzene ring less efficient, so the donating resonance effect is outcompeted by the inductive withdrawing effect. Also, empty d-orbitals of Cl, Br, and I account for additional resonance withdrawing effect. -GS).

If a substituent is a good electron donor, does that mean that the benzene ring is more reactive and willing to accept another substituent? (Yes, but only toward the SEAr reaction - GS). I think I am getting the para-ortho/ meta-directing groups mixed up with what a good activating and deactivating group is. How are these related? (Substituents are meta-directors only if have no electrondonating effects at all. All other substituents a o-,p-directors. Activating substituents are overall donors and deactivating substituents are overall acceptors. The resonance effect takes precedence over the hyperconjugative effect, which takes precedence over the inductive effect except for halogens, which are deactivating substituents. To avoid the most common mistake, consider the existing substituent, not the incoming one. - GS)

Could we go over what makes a good activating/deactivating group again? I still don’t understand the concept. (Donating electrons activates the ring toward an electrophile, withdrawing electrons does the opposite. - GS).

Why is the overlap of p orbitals in molecules with cyclic arrays of 4n pi electrons a destabilizing effect? (The highest occupied molecular orbital has higher energy and has same energy as the lowest unoccupied molecular orbital. - GS).

I read that a 1,4 addition more favorable than a 1,2 addition, but I don’t understand why? Wouldn’t the carbocation formed in a 1,4 addition be less stable than a 1,2 addition? Or is it because the carbocation is stabilized by resonance? (1,2-addition is faster, but 1,4-addition gives a more stable product. - GS),