Intro to Organic Functional Groups Lesson

this video is an introduction to the types of organic compounds and organic functional groups and there are a lot of them but this is just an introduction so what is an organic functional group well it’s not a complete compound but rather it is part of an organic compound often a reactive site in a compound for example ch3 something is part of many organic compounds including a small molecule such as methane here and including large molecules like an HEC tain carbon 100 hydrogen 202 and in this formula methyl group is part of that compound now students have organic chemistry you must memorize a variety of organic functional groups and the types of organic compounds that they form so let’s get started alkyl groups we’ve just mentioned the methyl group ch3 something as for example in the compound methyl chloride now if we have a methylene group it’s a ch2 group but that means there’s two more single bonds to something as for example in the compound methylene chloride and here’s a structure of it ch2 ccl2 chlorine is known to be a pale green gas and in these models cloying is represented by green atoms to carbonell kills an ethyl group would be the simplest ch3 ch2 something as for example in the compound ethyl chloride now we can also have an ethylene group which has two methylene groups and each one it has a single bond to some substituent as for example in the compound ethylene chloride here is ch 2 CL CH 2 CL methylene chloride a few more alkyl groups let’s look at three carbon al kills well straight chain alkyl n propyl group as for example in and pro pro quo ride is ch3 ch2 ch2 CL well it turns out that there is another isomer of the propyl group called an isopropyl group in which case the substituent is on the second carbon or the middle carbon as for example in the compound isopropyl chloride we have CH three chcl ch3 now whereas there were two different isomers of the propyl group there are in fact four different butyl isomers and have drawn for butyl chlorides below to illustrate this we’ll start with n-butyl chloride not n meaning normal or unbranched or straight chain as shown with the chlorine on the end this next structure is named isobutyl chloride now it’s butyl because there’s four carbons but why I so well in the numb in the nomenclature of the common system and there isn’t much but there are a few rules iso defines that a compound has a methyl group on the second last carbon from the end of the chain well what’s the beginning of the chain well the longest chain that contains the functional group is the main chain the head carbon is defined as the carbon bonded to the substituents so this marks the beginning of the chain here’s the end of the chain second from the end is a methyl group and that defines the ISO group isobutyl chloride there is also an isomer called sec-butyl chloride short from term secondary butyl chloride and sometimes abbreviated s hyphen butyl chloride notice in the structure that one of the internal carbons has a substituent on it now because this head carbon has bonded to two other carbons it’s defined as being a secondary carbon and the name sec-butyl chloride derives from that the fourth and final butyl isomer is named tert-butyl chloride if you look at the structure the head carbon is bonded to three other carbons and so that defines what’s called a tertiary carbon so the name can be tertiary butyl chloride sometimes written t-butyl chloride or even T hyphen beautiful

chloride let’s look at a couple of alkenyl groups taken from alkenes ch2 double bond CH something is defy is called a vinyl group an example would be vinyl chloride and here is the structure of vinyl chloride ch2 double bond chcl now vinyl chloride is a mala monomer that is polymerized to polyvinyl chloride a plastic often referred to simply as vinyl so rubber boots raincoats shower curtains and even vinyl siding on a home is generally polyvinyl chloride this next compound CH 2 double bond carbon with two substituents is referred to as a vanilla bean group an example would be vanilla tea in chloride CH 2 double bond CCL 2 and there’s the structure of vinylidene chloride another group that is similar but different than the vinyl group is called an allyl group some people call it an illegal group CH 2 double bond ch ch 2 CL is an example of allyl chloride so what’s the difference between allyl chloride and vinyl chloride well allele means that there is a substituent on a carbon next to a double bonded carbon whereas vinyl means that there is a substituent directly on the double bonded carbon let’s then look at some types of organic compounds we’ll start with the simplest now in these compounds are the letter R represents any alkyl group or sometimes simply the rest of the molecule an alkane is a saturated hydrocarbon it’s also referred to as a paraffin think of paraffin wax is a good example simple another simple example is propane and here is a structure ch3 ch2 ch3 all carbons are saturated with hydrogen alkenes have one or more carbon-carbon double bonds an alternate name for an alkene is an olefin which means attracted to few things or attracted by a few things and if you’ve smelled alkenes you know why few people are attracted to them simple example is propene CH 3 CH double bond CH to keep in mind always that carbon has four bonds a hydrocarbon with one or more carbon-carbon triple bonds is referred to as an alkyne simple example in its propyne and there’s its structure ch3 see triple bond CH our x where x is a halogen fluorine chlorine bromine or iodine is referred to as an alkyl halide occasionally called halo alkane there’s n-propyl chloride is an example of a simple alkyl halide ch3 ch2 ch2 CL aromatics sometimes called irene’s are compounds derived from benzene c6h6 now benzene is represented by all of the structures that are shown below in this structure on the left all carbons and hydrogen’s are showing other models our skeletal structures and is understood that there’s a carbon at the end of every line or at the junction of any two lines hydrogen’s are not shown these in these structures so benzene is a six membered hexagonal carbon ring it has an alternating pattern of single and double carbon-carbon bonds now in reality all six carbons share the six pi electrons there are three pi bonds to PI electrons per bond total of six pi electrons but they are not localized as the structure would indicate rather than having three single bonds and three double bonds benzene actually has six bonds which might be described as being one and a half bonds and these two illustrations on the right it’s served to show this that the six electrons the PI electrons are shared equally among the six carbons here we

have a phenol group c6h5 something that is referred to as an aerial group sometimes abbreviated AR when bonded now the benzyl group c6h5 ch2 is also shown here and it’s often confused with the fennel group they differ by this methylene group so try and keep them separate chlorobenzene c6h5 CL put a chlorine on here and benzoyl chloride c6h5 CH 2 CL put a chloride on here are examples of aromatic compounds ethers have an oxygen atom that is singly bonded to two alkyl groups as illustrated in this structure now the oxygens bonding in an ether is very similar to an oxygens bonding and water and so the basicity of an ether PKB about 17 is similar to that of the basicity of water it’s the same oxygen donating the same-ish pair of electrons however the acidity of an ether is quite different ethers are completely non-acidic ethers do not have the hydroxyl hydrogen to donate and as a result of that you’ll sometimes see either is used as solvents in reactions where using a very strong base which would otherwise deprotonate other solvents like alcohols which have hydroxyl hypertens diethyl ether fo oxygen ether is a common organic solvent ch3 ch2 oh ch2 ch3 so oxygens are depicted red in these models diethyl ether is nonpolar it’s dielectric constant is only for it has a low boiling point 35 degrees C that makes it a good solvent general purpose solvent in the organic laboratory so you can use ethers to extract organics out of water the ether will separate from water in a separatory funnel being less dense it’s the upper layer you can then separate them the two layers take the ether layer dry it and then evaporate off the ether relatively quickly the blowing points35 and recover your product organic peroxides now peroxides contain the oxygen to oxygen single bond group there are two kinds we have died alkyl peroxides RoR and hydro peroxides are olh here’s an example dimethyl peroxide and here’s a hydro peroxide t-butyl hydro peroxide both of these are analogous to hydrogen peroxide the peroxide bond is weak only about 50 kilo Cal’s per mole that makes it reactive and unstable especially when you think of the strength of an oxygen to carbon bond or an oxygen to hydrogen bond typically in the range of 90 to 100 killa kellz per mole so a lot of heat can be released when an oxygen the oxygen peroxide bond is broken and an oxygen to carbon or oxygen to hydrogen bond is formed instead now peroxides cleave homolytic ly producing two free radical groups so here is the peroxide bond cleaning homiletic allah meaning breaking evenly notice one electron going in each direction these fish hooks these half arrowheads indicate the transfer of one electron producing in this case at all coxy free radical there’s the free radical the unpaired electron and the hydroxy free radical alcohols ROH are similar to water not only in their structure but also in their acid-base chemistry water is a very weak acid its PKA is 15.7 for it’s also a very weak base pkb 15.7 for likewise alcohols are very weak acids pKa approximately 16 and very weak bases pkb approximately 16 as well ethanol and there’s a structure of it ch3 ch2 o h is the alcohol of beverages aqueous solutions of isopropyl alcohol here it is CH 3 CH 0 h CH 3 here again we see this isopropyl group thirty to seventy percent aqueous solutions of isopropyl alcohol are sold in pharmacies under the name rubbing alcohol don’t think that the uncharged hydroxyl group of an alcohol for example here is even

remotely close to the hydroxide group oh h minus of the hydroxide ion c whereas the hydroxyl groups of water and of alcohol are neutral the hydroxide group in sodium hydroxide base PK b- 1.74 this is a good electron donor negative charge makes a huge difference next we’re going to look at phenols now this compound c6h5 o-h is a specific compound called phenol but phenols are actually a class of compounds that are derived from phenol here’s an example of a phenol a phenolic compound common name is parekh wrestle and parekh wrestle wikipedia tells me is the major component of pig odor present in human perspiration and believed to be the component of human odor that is attractive to female mosquitoes now if you look at the structure of an alcohol and a phenol they look alike but chemically they’re different alcohols are weak acids they have a pka of about sixteen but phenols are actually mildly acidic their PKA is approximately ten that’s a large difference PK values are powers of ten we’re saying that a phenol is 10 to the sixth or a million times more acidic than an alcohol and so whereas alcohols will not react with sodium hydroxide a phenol will react with it neutralize it if you will acting as an acid and dissolve in strong bases like sodium hydroxide here’s an example of that chemical reaction sodium hydroxide the hydroxide ion is a pkb of negative 1.74 phenol itself has a pka of nine point nine our base is the electron pair donor donating pair electrons to form a bond with the acidic hydrogen in phenol hydrogen is mono valent it can’t have two bonds at the same time if it’s going to form a bond to oxygen then it has to break the bond but is currently has with phenol that liberate seeeeee water and gives us the conjugate base sodium phenoxide now the phenoxide ion is another functional group its pkb is for its a moderately strong base since we’re talking about acids let’s look at the most common organic acids called carboxylic acids our carbonyl o-h now the hydroxyl group in a carboxylic acid is acidic because it is bonded to the carbonyl group the carbonyl groups are electron withdrawing it changes the game we don’t have carbonyl groups in water or in alcohols and those hydroxyl groups are not acidic but in a carboxylic acid in fact it is acidic typically they have a pKa of approximately five this is a structure of acetic acid ch3 carbonyl o.h it has a pKa of 4.7 and it will react completely with strong bases like sodium hydroxide producing the acetate ion which is an example of a carboxylate ion here’s the acetate ion ch3 carbonyl Oh minus without as hydrogen ion do you recall the general acid based mechanism here’s our base electron pair donor here is our asset electron pair acceptor the base will donate a pair of electrons to the hydrogen ion the hydrogen in the acid hydrogen is mono valent and can’t have two bonds at the same time so it has to break a bond with a and so the base becomes bh the conjugate acid of the base at the same time h a becomes a minus the conjugate base of this acid so let’s try that on a specific example here’s a carboxylic acid and here’s the hydroxide ion carboxylic acids in general have a pKa of approximately five hydroxide i- 1.74 what’s the mechanism going to look like the base will donate a pair of electrons any one of these three pairs is identical to the hydrogen the acidic hydrogen in the carboxylic acid hydrogen is mono valent can only form one bond at a time so that means it has to break this bond to the carboxylic oxygen in order to form a bond to the hydroxide water is the product and a carboxylate

ion now the PKB of the carboxylate ion is 14 minus the pKa 14 minus 5 is 9 and so this is basic enough that we can reverse the reaction by reacting with a strong acid such as the hydronium line PK a negative 1.74 notice that the pKa of the hydronium ion is equal in magnitude to the PKB of the hydroxide ion not surprising since the pKa and the PKB of water is the same 15.7 for in any case here’s the reaction mechanism our base donates a pair of electrons to the acidic hydrogen hydrogen is mono valent it has to break a bond with vibranium I on to form the bond of the carboxylate so water is produced and the carboxylic acid is reformed acid anhydride are just what their name implies acids without water there is a structure of an acid anhydride our carbonyl whole carbonyl are now in and hydrides the R groups r 1 r 2 they can be the same or different alkyl groups how do you form an anhydride vigorous heating will dehydrate a carboxylic acid if you take a look at the reaction here a total of one mod one water molecule is removed for every two molecules of the acid so here I have two molecules of acetic acid it’s heated up water is eliminated to produce the anhydride in this case acetic anhydride because it’s formed from acetic acid and here is the structure of acetic anhydride ch3 carbonyl Oh carbonyl ch3 siegen hydride is probably the simplest and most common acid anhydride uslan lab this reaction you may have noticed is reversible when you take an anhydride and heat it with water then the water molecule will add forming two carboxylic acids acid and hydrides are very reactive organic electrophiles meaning electronic scepters they are therefore often used in organic synthesis reactions esters are next an ester is our carbonyl oor now the structure looks similar to a carboxylic acid except we have an R group instead of a hydrogen now the R groups the two R groups and Esther can be the same or different esters in fact are often synthesized by reacting a carboxylic acid with an alcohol in the presence of an acid catalyst that’s called the Fischer esterification reaction here’s an example methyl butano ate the flavor of apples forms when butanoic acid reacts with methyl alcohol here’s the reaction ch3 ch2 taken twice carbon loh that’s butanoic acid reacting with methanol in the presence of acid and a hydrogen ion catalyst will condense out water now notice that’s not an acid-base reaction because it is the acid is not losing a hydrogen ion in fact though the acid is losing the hydroxyl group and it’s the alcohol is losing the hydrogen ion so it really isn’t any sort of an acid-based reaction condensation occurs we get the methyl ester butanoic acid methyl butan 08 now the reaction yield is typically about fifty percent more with small with small acids and alcohols and it’s a little bit less with large acids and alcohols and it’s also reversible you may have noticed if I add water to the system rather than boil it out heat it and add an acid catalyst the reaction goes in the reverse forming the carboxylic acid in the alcohol this is simply less chatelier’s principle at work next group is an a seal group our carbonyl something the ACL group like the carbonyl group is an incomplete compound that is it’s part of several classes of organic compounds such as the acid halide also known as the ACL halide now acid halides they’re one of the most reactive electrophiles electronic scepters in organic chemistry and they’re used to carry out very quickly a

lot of organic reaction syntheses that otherwise would require long reaction periods now the x and the acid halide represents any halogen however in practice the halogen is usually not part of the reaction product and so the least expensive acid halide that would be the acid chloride is almost always used and here is the structure of an acid chloride our carbonyl CL as a teal chloride ch3 carbonyl CL acetyl chloride and benzoyl chloride c6h5 ce o– CL are too common a sealed halides the formal group also known as the method oil group is again part of other compounds H carbonyl something and one of the groups are going to look at next that the formal group is part of is our aldehydes and aldehydes have an R group attached the formal group so it’s our carbonyl H aldehydes are flavorings and they are fragrances here’s an example propionaldehyde a three carbon aldehyde ch3 ch2 carbonyl H has a fruity flavor benzaldehyde c6h5 carbonyl H has an overpowering cherry odor now this particular aldehyde formaldehyde is a bit of an exception to the structure rule it has one carbon but it has two hydrogen’s and no our group it’s the simplest possible aldehyde it’s the only aldehyde that doesn’t have an alkyl group attached to it so from aldehyde was formerly used to preserve biological specimens but it’s been largely replaced since being designated a known carcinogen ketones are next ketones have the structure our carbonyl are similar to aldehyde except two alkyl groups instead of one several ketones are produced by the human liver from fatty acids during periods of low food intake aka fasting or from carbohydrate restricted diets and I have here the structure and a model of acetone dimethyl ketone commonly called acetone is important it’s miscible in water dissolves many organic compounds as well and it’s a good general purpose solvent particularly because of its high volatility its boiling points only 50 degrees Celsius and so glassware rinsed with acetone dries quickly well let’s look at some organic bases and alkyl amines are certainly the most common organic base and they’re very similar to ammonia an alkylamine simply has one or more of its hydrogens replaced by alkyl groups hero is a primary amine it has one alkyl group replacing a hydrogen or we could say there is one carbon bonded to the central nitrogen a secondary amine has two carbon groups bonnet of nitrogen a tertiary amine has three alkyl group spawn into nitrogen this last structure actually has 4 alkyl groups volatile nitrogen such that the nitrogen is no longer neutral it’s a nitro neum cation and this group as a whole is called a quaternary ammonium cation and so primary secondary tertiary and quaternary alkyl amines respectively have one two three or four alkyl groups attached nitrogen and when I say quaternary alkyl amines I do it in the spirit in which it’s commonly used but we understand that it’s not truly an amine any longer it’s an iminium cation once its quaternary now ammonia is moderately basic its pkb is 4.8 and so are the neutral a means the fact is slightly more basic typically about pkb for the quaternary iminium cation will be acidic much like ammonia mine is acidic and affect its PKA is approximately 10 so let’s look at an acid-base neutralization reaction we’re going to use methylamine as our base it’s pkb is 3.4 and will react it with hydronium ion who is PK a is negative 1.7 for now the

base is the amine it’s got the non bonded pair of electrons which it can donate to any one of the three city captions in hydronium ion hydrogen is monoprotic if it’s going to form a bond with nitrogen it’s going to have to break its bond to oxygen that will produce the methyl ammonium cation and by-product is water now the methyl ammonium cation is the conjugate acid of the amine we can calculate its PKA it’s 14 minus the pka of the conjugate base so 14 minus 3.4 is 10.6 we can reverse this reaction by reacting with hydroxide ion peak a b- 1.7 for a strong base any one of its three non bonded pairs of electrons can form a bond with one of the acidic hydrogen’s if hydrogen is going to form a bond with oxygen it has to break it spawned to nitrogen because hydrogen is always mono valent the product will be methylamine and by-product water ariella means they’re like alkylamines there’s an amino group bonded to an aromatic ring so here we have a primary area lamine with one aerial group bonnet and nitrogen a secondary area lamine has two area groups bond to nitrogen a tertiary aerial amine has three ariel groups bonnet of nitrogen and when we have for aerial group sponsored nitrogen this would be a quaternary aerial iminium cation so analogous to alkyl amines aerial amines have primary can be primary secondary tertiary or quaternary when they have one two three or four aerial groups attached to nitrogen this is annalynne c6h5 nh2 it’s a common aerial amine now aerial amines are much weaker basis than alkyl amines and that’s why they’re presented separately here annalynne for example has a pkb of 9.3 and this is because the nitrogens the non bonded electrons on the nitrogen are tied up in the aromatic ring when you show it here these pair of electrons are tied up in the aromatic ring and they’re less available for donation to an acid making an aerial I mean much less basic an alkylamine adeline however is basic enough that will react with a strong acid like hydronium ion and let’s show the mechanism for that annalynne with a pkb of 9.3 and I drone in line with a pkb pKa of negative 1.74 will react completely nitrogens non bonded pair of electrons is the base it’s going to donate the pair of electrons to any one of the three acidic hydrogen see in a hydronium if that hydrogen is going to form a bottle of nitrogen it has to break its bond with oxygen because hydrogen is mono valent and so as nitrogen forms a bond forming the and the linnean chloride cation at the same time hydronium ion is converted to water now the pKa of the N linnean chloride cation is 14 minus the PKB of its conjugate base 14 minus nine point three is four point seven and so this reaction could be reversed as well using a strong base let’s look next at a mites our carbonyl nh2 now a mites contain both an amino group and a carbonyl group a primary a mind has one carbon group attached some nitrogen a secondary amide has two carbon groups volatile nitrogen and a tertiary a mine has three carbon groups bonded to nitrogen so primary secondary and tertiary amides have one two or three carbon groups bonded to nitrogen respectively despite their similarity to amines in name and appearance amides are not basic instead they are similar to alcohols being either basic nor acidic you see the non-bonded nitrogen electrons that are basic and amines are tied up by the adjacent electronegative carbonyl group so the less available to be donated to acids amides therefore are

quite neutral they are relatively stable and unreactive compounds a mines are pervasive in nature in technology as structural materials for example nylon plastics Kevlar protein hair spider silk the name a few are long-chain polyamides here is the structure of us acid amide ch3 carbonyl NH 2 because of its low molecular weight it’s a low melting solid used as a plasticizer and a soluble Iser it increases the solubility of many other chemicals nitriles naturals have the structure are see triple bond n now the prefix ino is often used interchangeably with the term nitrile in industry in organic compounds that contain the same group C triple bond and are called cyanides for example here’s hydrogen cyanide potassium cyanide would be another example nitriles are relatively stable unreactive compounds and pH neutral naturals are found in many useful compounds including cyanoacrylates the super glues and nitrile rubber gloves that are used often in latex free laboratories here is a commercially important nitrile aquila nitrile ch2 double bond CH c triple bond n this monomer is polymerized to make polyacrylonitrile fiber which is used in the manufacture of clothing under the trade names acrylic and/or lon nitro compounds contain the no.2 group bonded to an alkyl group inorganic salts that contain the same group are termed nitrates many nitro compounds and nitrates are in fact made from nitric acid now you want to notice that in both nitrates and in the organic natural compound the no.2 group contains the negatively charged oxygen and a positively charged electronium cation while the whole time the Nano to group is overall neutral you probably are aware that highly nitrated compounds are very explosive and I have two structures to show hear of such this is trinitrotoluene on the right three nitro groups on a toluene ring aka dynamite and here’s nitroglycerin and that’s probably enough for an introduction to organic functional groups