CHEM219 / CHEM 219 Module 2: (Latest Update 2026 / 2027) Principles of Organic Chemistry with Lab

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CHEM219 / CHEM 219 Module 2: (Latest Update 2026 / 2027) Principles of Organic Chemistry with Lab | Questions & Answers | Grade A | 100% Correct – Po ... rtage Learning 2026 / 2027 Academic Year Q: Two types of reactions for Alkanes Answer Combustion (oxidation) and Radical Halogenation (substitution) Q: What does Combustion reaction produce? Answer CO2 and H2O Q: Is Combustion Endothermic or Exothermic? Answer Exothermic Q: What is exothermic? Answer Heat (energy) is released Q: The greater the number of carbons in an alkane, the _______ the amount of heat released in the combustion reaction Answer GREATER Q: Is the enthalpy (delta H) positive or negative in a combustion reaction? Why? Answer Negative because heat is being released Q: Why is a combustion reaction also called Oxidation? Answer Carbon is combining with oxygen Q: What occurs during a radical halogenation reaction? Answer Halogen atoms replace hydrogen atoms on an alkane molecule Q: Why is Radical Halogenation considered a Substitution reaction? Answer Because halogen atoms substitute hydrogen atoms on the alkane Q: What is the catalyst for Radical Halogenation? Answer Heat or UV Answer More than 1 H atom is replaced by a halogen Q: Halogen radicals in Radical Halogenation Answer Species with a single unpaired electrons that attack the alkane substrate to pull off hydrogen atoms and substitute themselves in their place. Q: Polyhalogenated products Q: Name the 5 "Addition" reactions in alkenes/alkynes Answer Addition reaction Halogenation Hydration Addition of Acids to Alkenes Addition of Hydrogen to Alkenes Q: Name the two oxidation reactions in alkenes/alkynes Answer Oxidation with Potassium Permanganate Ozonolysis Q: Why are addition reactions in alkenes thought of as combunations? Answer Two different molecules join to form a single new compound Q: What happens to the pi bond of the alkene in addition reactions? Answer It is broken Q: What happens to the sigma bond of the reagent in alkene addition reactions? Answer It is broken Q: What does the C atom in addition reactions gain? Answer 2 new sigma bonds Q: How does the geometry of the alkene in addition change? Answer Goes from Trigonal planar to tetrahedral Q: Is the product of alkene addition saturated or unsaturated? Why? Answer Saturated because no new bonds can be made. Q: Halogenation product for alkenes Answer Alkyl Dihalide Q: Why do alkenes readily add halogens? Answer Because it is energetically favorable to do so (due to enthalpy) Q: What happens during a Br Qualitative Test for Alkenes? Answer Br is typically red/brown in color, but when it bonds with alkene, it is dibromoalkane and it is colorless. If you drop Br into a random substance, you will know it is alkene if the color changes to colorless. Q: What happens in the Hydration of Alkenes? Answer Alkenes add a water molecule across the double bond in the presence of an acid catalyst. Q: What is the product of the hydration of an alkene? Answer Alcohol (-OH) Q: Why is an acid catalyst needed in the hydration of alkene? Answer Neutral water molecules are not reactive enough to start a reaction on their own Q: What does H and A stand for with H-A? Answer H = acidic proton A = remainder of the acid What is the qualitative testing in Acid Addition? Q: What is the product of Hydrogenation in Alkenes? Answer Alkane Q: What happens during Hydrogenation of an Alkene? Answer The unsaturation is removed Q: Where does Hydrogenation of an alkene occur? Answer On metal surface Q: Does Hydrogenation of alkenes produce mainly cis or trans stereoisomers? Answer Cis! Q: What is the product in Oxidation w/ KMnO4? Answer Glycol Q: What setting is Oxidation w/ KMnO4 performed under? Answer Basic conditions and relatively cool temps Q: Do Alkenes react readily with aqueous solutions of KMnO4? Answer Yes Q: What is the qualitative test undergone through Oxidation w/ KMnO4? Answer The royal color of the permanganate solution disappears and a brown precipitate of MnO2 appears. This is to distinguish alkenes from alkanes. Q: What is the product of Ozonolysis? Answer Carbonyl groups Q: What occurs during Ozonolysis? Answer Alkene reacts with O3 (Ozone) Q: What is O3's relationship to Oxygen? Please elaborate on the term used Answer Allotrope - Different physical form that an element can exist What is the catalyst in Ozonolysis? Answer Zinc Metal and aqueous acid What happens to the C=C in Ozonolysis? Answer It is cleaved What is the qualitative testing of Ozonolysis? Answer Looking at what atoms or groups are attached to in the carbonyl groups to see where in a chain the double bond is present. This allows for reconstruction of the original alkene. Why do alkenes readily react with oxidizing reagents? Answer High electron density of the double bond What happens in an oxidation reaction of alkenes? Answer The oxidizing agents attack the pi-electrons of the double bond Are aromatic rings stable or unstable? What does this mean? Answer Aromatic rings are stable, which means they have a lack of reactivity What does it mean that aromatic rings are conjugated? Answer Separated by only 1 C-C sigma bond. How are aromatic rings thought of in regards to their conjugated bonds? Answer INFINITE LOOP Repeating pattern of pi - sigma - pi Why do aromatic rings not get involved with reactions? Answer The need for preservation of the pattern. What does EAS stand for? Electrophilic Aromatic Substitution What is an electrophile? Electron-deficient chemical species that seeks electrons What happens during EAS reactions? Electrophile attacks the ring, bonds to carbon to temporarily disrupt the aromaticity. The aromaticity is then restored by chemical species that removes a H atom and donates the electrons from the C-H bone back to the ring restoring the aromaticity. list prefixes for first 10 carbons in order meth, eth, prop, but, pent, hex, hept, oct, non, dec hydrocarbon compounds composed of only carbon and hydrogen parent chain longest continuous chain of carbon atoms alkane (with formula) hydrocarbon containing only single bonds between carbons, CnH2n+2 substituent heteroatom or group of atoms that are attached to the parent chain numerical prefixes for # of identical substituent groups (2-10 in order) di, tri, tetra, penta, hexa, hepta, octa, nona, deca rules for naming alkanes 1. longest continues chain is parent chain 2. number parent chain starting with the end closest to the first branch 3. name using IUPAC rules for substituents IUPAC systematic name order for alkanes locant-(prefix)SubstituentParent in numbering parent chains, if there are two equally long chains... select the chain with the most branches coming off in numbering parent chains, if the first branch point if the same distance from either end of the parent chain... choose the numbering that gives the lower numbers to the most substituents in numbering parent chains, if there are only 2 substituents and both are equidistant from opposite ends of the parens chain... choose the numbering direction so the substituent with the higher alphabetical priority gets the lower locant number solubility and density properties of alkanes NOT soluble in water, low density (< 1g/ml) so floats on top of water melting and boiling points properties of alkanes LOW MPs and BPs due to weak attractive forces between molecules how does branching affect MPs and BPs branching lowers surface area of the molecule, which in turn lowers VDWFs and thus lowering BPs and MPs conformers different shapes of molecules derived from rotations of single bonds staggered conformation H atoms do not overlap in line of sight (more stable) eclipsed conformation heteroatoms overlap with one another (less stable) rotamers conformers that can be swapped with a simple rotation of the C-C bond what conformation do molecules prefer? molecules adapt conformations that minimize repulsion, so likely staggered (zigzag formation) cycloalkane alkane whose carbon skeleton is in a ring how to name cycloalkanes add prefix "cyclo" to the parent chain portion of the name when naming cycloalkanes, if ONE substituent is present... NO locant numbers are added and the substituent name is added in front of the parent name (methylcyclobutane) when naming cycloalkanes, if more than one substituent is present... carbons on the parent ring are numbered, starting with the carbon with the substituent group with the highest alphabetical priority and continuing in the direction that gives the other substituents the lowest locant numbers (1-ethyl-2-methylcyclohexane) angle strain occurs when the actual bond angle in the ring is not what VESPR predicts for the atom's electron geometry angle what is the most stable number of carbons in a chain? Why? 6, because C6 has bond angles that almost match the VESPR prediction of a tetrahedral bond angle torsional strain strain from eclipsed conformations, occurs when a ring is planar and has no choice but to have all carbons on the same plane non-planar conformations slight rotations in C-C bonds to move the carbons from all being on the same plane puckered conformation 2 carbons fold out from the other 2 in a C4 envelope conformation one carbon folds up in C5 chair conformation one carbon tilts up and one on the other end of the ring tiltds down in C6 stereoisomerism different compounds with the same connectivity but different positioning of atoms or substituent groups in 3D space reactivity properties of alkanes typically inert, do not react with most acids, bases, or oxidizing/reducing agents combustion of alkanes properties exothermic, results in CO2 and H2O, the more carbon in the alkane, the more heat is released heterocyclic molecules where at least 1 atom in a ring is NOT carbon (mostly O, N and S) radical halogenation reaction using heat or UV light where a halogen atom replaces a hydrogen atom in an alkane molecule R-H + X-X --> R-X + H-X polyhalogenated products occur when more than one H atom is replaced by a halogen due to excess of the halogen, causing a mixture of all the different possible halogen substituted products list two main types of reactions in ALKANES combustion and substitution (radical halogenation) what causes unsaturation vs saturation unsaturation occurs when the number of H per C is lower than for saturated carbons, and occurs in double bonds as the double bond on the C takes away the possibility of H atoms being able to bond carbocyclic molecules with at least 1 ring of all C functional group group of heteroatoms in a specific pattern attached to an organic molecule that leads to certain reactivity and physical properties electrophilic aromatic substitution substitution where an electrophile (chem substance seeking electrons) replaces an H. instead of addition the (+) electrophile removes an H resulting in the E attached to the ring and an A-H leftover aliphatic hydrocarbons alkanes, alkenes, alkynes aromatic hydrocarbons -arenes, such as benzenes lack of reactivity very stable conjugation double bond separated by 1 sigma bond when 3 or more substituents are present on a benzene the locant numbers are used to describe the position (1,2,4-trimethylbenzene) polycyclic aromatic hydrocarbons more than one benzene ring fused together with each ring sharing 2 or more of the same C atoms in naming monosubstituted benzenes name of substituent group is added to parent name "benzene" (clorobenzene) when 2 substituents are present on a benzene use prefixes to describe location of substituents in relation to one another (o-dichlorobenzene) prefixes for locating 2 substituents on a benzne (o) ortho = 1 carbon away (m) meta = 2 carbon away (p) para = 3 carbon away place letter instead of locant number benzene C6H6 ring with alternating double bonds what reaction is used to pinpoint specific location of double bond? How? ozonolysis, O3 acts like scissors and breaks the double bond apart creating two carbonyl compounds attached to the 2 parts of the molecule how is bromine used in alkene/alkyne reactions if the orange/brown color of the bromine disappears when added to a compound the molecule is an alkene/alkyne typical reaction type for alkenes and alkynes addition reaction where atoms or groups of atoms are added to each carbon in the multiple bond, causing the bond to become single or double two major classes of hydrocarbons aliphatic (alkane, alkene, alkyne) and aromatic (benzene) how does surface area impact MPs and BPs greater surface area means more VDWFs which leads to higher MPs and BPs how to determine if cis/trans isomerism is possible around a double bond if the substituent comes off on the same side it is cis, if on the other side it is trans, if the sides look different it is not possible what are the two qualitative reactions for the presence of an alkene Bromine addition (if color disappears it IS an alkene) AND oxidation with KMnO4 (if purple color disappears and leaves brown precipitate it IS an alkene) why do aromatic rings undergo substitution and NOT addition? the loop of conjugation (pi-sigma-pi) causes great stability, substitution occurs rather than addition because addition would break the stability of the ring list IUPAC steps for naming alkenes/alkynes 1. select parent chain that contains both carbons in multiple bond 2. number locants so the multiple bond has the lower numbers (if equidistant number with 1 closer to 1st branch) 3. indicate multiple bond using lower locant number (2-hexene NOT 3-hexene) in naming alkenes/alkynes if more than one pi bond is present... number the patent chain from the end nearest to the first pi bond is a double C bond and triple C bond are present AND equidistant from the ends number locants... so that the double bond gets the lower numbers how to name cyclic alkenes/alkynes without substituents no locant numbers needed (cyclohexane) how to number cyclic alkenes/alkynes with substituents number so the multiple bond contains number 1-2 and the substituents get the lowest numbers

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