Topic 10: Organic Chemistry Flashcards
What is a homologous series?
A series of continuous compounds of the same family with the same general formula, which differ from each other by a common structural unit
What trend to members of a homologous series show for physical properties?
Gradiation in physical properties within the series due to gradual increase in weight and size, like boiling points
What trend do members of a homologous series show for chemical properties?
Similar chemical properties within the series as all compounds in the series have the same functional group (the reactive part)
Successive members of a homologous group differ by…
1 CH2 group
How are members of a homologous series named?
Prefix (number of C atoms in longest chain) and suffix (homologous series to which the compound belongs)
What are the three homologous series?
alkanes, alkenes, alkynes
What is an alkane? What suffix and formula are used?
Saturated hydrocarbons with only single C-C bonds. C(n)H(2n+2). Suffix: -ane
What is an alkene? What suffix and formula are used?
Unsaturated Hydrocarbons with at least one double carbon carbon bond. C(n)H(2n). -ene
What is an alkyne? What suffix and formula are used?
Unsaturated hydrocarbons with at least one triple carbon carbon bond. C(n)H(2n-2). -yne
List, in order of 1-10, the prefixes used to determine the number of carbon atoms in the longest carbon chain
1: meth
2: eth
3: prop
4: but
5: pent
6: hex
7: hept
8: oct
9: non
10: dec
What is the formula for a methyl, ethyl, and propyl group?
Methyl: CH3
Ethyl: CH2CH3
Propyl: CH2CH2CH3
For a cyclic alkane, what prefix is added?
cyclo-
What are four other rules for naming organic molecules?
Use the longest Carbon chain when naming. Groups go on the lowest number carbon. Organize groups by alphabetical order. Use di, tri, tetra, penta, and hexa to determine the number of the same functional group
Functional groups determine…
The specific chemical properties of a molecule, which in turn determines the kind of reactions it undergoes
What is benzene? What is its structural formula? What is its C:H ratio, and why is that significant?
An aromatic, unsaturated hydrocarbon w/ formula C6H6. 1:1 ratio of C:H means that it is even more unsaturated than alkenes or alkynes
Benzene molecules are also named…
They are called “aromatic” because…
Do benzene molecules have isomers? Do they undergo addition reactions?
Arenes. Aromatic because they are typically fragrant. No isomers. Reluctant to undergo addition reactions.
What is a structural isomer? Give an example.
Molecules that have the same formula but different atomic arrangement, therefore unique properties. Ex: C4H8 can be 1-butene or 2-butene, depending on where the double bond is.
The drawing of a benzene ring shows alternating C-C and C=C bonds. What is the actual structure of a benzene ring?
Reasonance hybrid. It has equal bond lengths that are the average of the double and single bond lengths.
What is an electrophile? How does that relate to benzene?
An e- deficient species. Benzene can undergo electrophilic reactions in which a Hydrogen is replaced by another group
What is homolytic bond fission?
A covalent bond breaks with each atom taking one e- from the bond. Results in the formation of highly reactive free radicals with unpaired e-
What is heterolytic bond fission?
A covalent bond breaks and one atom takes both e-. Results in the formation of an anion and a cation. The more electronegative atom usually takes the 2e-.
What is the difference between primary, secondary, and tertiary carbon atoms?
Primary carbon atoms are bonded to zero or one other C atom.
Secondary is bonded to two other C atoms.
Tertiary=3 other C atoms
Are alkanes typically reactive? Why or why not?
Relatively unreactive due to strong, nonpolar C-H bond
Can alkanes undergo combustion?
Yes
What does alkane combustion produce?
CO2, H2O (if oxygen is in excess)
What color flame does complete combustion produce?
blue
Why are bigger hydrocarbons less likely to completely combust? What color flame do they produce?
They have more Van der Waals forces, making them harder to vaporize. They often burn yellow/smokey.
What is CO?
Carbon monoxide. A colorless, odorless, toxic gas that binds to create a hemoglobin that prevents oxygen from being carried to the blood. Leads to suffocation
What are the different products of complete and incomplete alkane combustion?
Complete: CO2 and H2O
Incomplete: CO and H2O
What is the formula for a complete combustion reaction?
CxHy + O2 —> CO2 + H2O
What is the formula for an incomplete combustion reaction?
CxHy + O2 —> CO + H2O
What is a free radical substitution reaction for alkanes? What are the most common free radical substitution reactions?
A reaction in which atom(s) are replaced by different atom(s). Most common is halogenation, in which H atoms are replaced by a halogen
What catalyst is usually present for halogenation?
UV light
What are two examples of halogenation?
Chlorination, bromination
What are the three steps of halogenation/free radical substitution?
Initiation, propagation, termination
What are free radicals?
A highly reactive species with an unpaired e-
What is the initiation step of free radical substitution?
Requires UV light. Photochemical homolytic fission occurs when bond between halogen atoms is broken, creating 2 free radicals. Ex: Br2 —> Br. + Br. (Bromine radical)
What is the propagation step of free radical substitution?
A hydrogen atom within the molecule bonds with the radical, producing a different free radical, which will react to form another molecule and free radical. This can continue to react.
Ex: CH4 + Br. —> HBr + CH3. (CH3 radical)
What is the termination step of free radical substitution?
Free radicals react to form other molecules. Stops when there are no more molecules.
In which steps of free radical substitution does the number of free radicals increase, decrease, or stay the same?
Increases in initiation, stays the same in propagation, decreases in termination
What is a test that can be done to determine if a molecule is unsaturated? (i.e. it is not an alkane?)
Bromine water is brown colored and can be used to distinguish between alkanes and alkenes. Alkenes are more reactive due to the C=C bond, so they react w/ Br water to decolorize it and form an alkane w/ 2 Br functional groups. Alkanes do not react w/ Br water
What are halogenalkanes?
They contain an atom of F, Cl, Br, or I. They are more reactive than normal alkanes and can undergo nucleophilic substitution or elimination reactions.
What type of reactions do primary halogenalkanes undergo?
Substitution
What type of reactions do secondary halogenalkanes typically undergo?
Both substitution and elimination
What type of reactions do tertiary halogenalkanes typically undergo?
Mostly elimination
Describe elimination reactions for halogenalkanes.
Removing a small molecule, often H2O, in the presence of Na or KOH
What are substitution reactions? What are nucleophiles?
Substitution: swapping a halogen atom for an -OH group to form an alcohol. Nucleophiles: An e- rich species that can donate a pair of e- to an e- deficient carbon, forming a covalent bond
What happens during a substitution nucleophilic reaction for a halogenalkane?
The halogenalkane is heated under reflux with a solution of Na or KOH. OH- behaves as a nucleophile to form alcohols. Halogen is more electronegative than C, so it forms a polar bond.
What is heating under reflux?
Heating with a condenser placed vertically in the flask to prevent the loss of volatile substances
What is an electrophilic addition reaction for an alkene?
Two molecules combine to produce a larger molecule, breaking the double bond.
What are four types of electrophilic addition reactions that alkenes can undergo?
Hydrogenation, hydration, halogenation, addition polymerization
What is a hydrogenation reaction w/ an alkene?
Alkene reacts w/ H to form an alkane. C=C becomes C-C, H2 becomes H and H attached to carbon
What is an example of a hydrogenation reaction?
H2 + C2H4 —> C2H6
What is a hydration reaction w/ alkenes?
Alkene reacts w/ steam to form an alcohol, C=C becomes C-C, H2O becomes H and OH attached to C
What is an example of a hydration reaction?
H2O + C2H4 —> C2H4OH
What is a halogenation reaction with alkenes? Give an example.
An alkene reacts w/ a halogen to produce dihalogen compounds. C2H4 + Br2 —> C2H4Br2
What is an addition polymerization rxn w/ alkenes?
Addition polymers are formed when smaller unsaturated molecules (monomers) react together. The small monomers w/ C=C link together to form a longer polymer, breaking the double bond.
Why do alcohols have increased solubility? Where do alcohol reactions take place?
OH (hydroxyl) group is polar, increasing the solubility of alcohols in H2O. Reactions mainly occur at the functional group, but some involve H atoms attached to -OH
Oxidation reactions with alcohols usually form…
aldehydes, ketones, and carboxylic acids
Oxidation with primary alcohols
produces aldehydes, further oxidized to carboxylic acids.
Can tertiary alcohols be oxidized?
No.
Oxidation with secondary alcohols
produces ketones
What is the formula for combustion of alcohols?
CxHyOH + O2 —> CO2 + H2O
What is an esterfication reaction with an alcohol?
esters are formed when carboxylic acids react with alcohols in the presence of H2SO4.
How can you determine the original alcohol and acid after an esterfication reaction?
The ester’s name gives clues. Ex: ethyl propanoate is made from an ethanol group and propanoic acid.
