Ch 8 Nomenclature and Noncovalent Intermolecular Interactions Flashcards
Alkyl Halide
halogen is bound to alkyl group
common name: alkyl group name + halide name after
IUPAC: normal alkene/alkane naming, halides as substituents (fluoro, chloro, bromo, iodo
BP: have significant dipole moments but low BPs
*have greater density than Alkanes (small volume and less surface area) = lower van der Waals ((as compared to Alkanes of similar mass))
Alcohol
compound with hydroxy (-OH) group bound to carbon of an alkyl group
common name: alkyl group to which -OH is attached to + ‘alcohol’
IUPAC: find principal group, find principal chain, number the carbons in terms of priority (principle groups, multiple bonds, substituents, first cited substituent); cite principal number last, no principal group -> substituted hydrocarbon, alphabetical order!
More than one -OH? diol, triol (don’t lose the e of the alkane!) – if it’s just one OH, lose the e
BP: unusually high
Thiol
compound with a mercapto group or sulfhydryl group (-SH) bound to the carbon of an alkyl group
Common name: alkyl + ‘mercaptan’
IUPAC: find principal group, find principal chain, number the carbons in terms of priority (principle groups, multiple bonds, substituents, first cited substituent); cite principal number last, no principal group -> substituted hydrocarbon, alphabetical order!
Phenol
-OH bonded to C of an aryl group (benzene with another bond – as opposed to the OH being bonded to that previous R-group: alcohol)
Enol
-OH bonded directly to an sp2 hybridized C (instead of to an R-group that’s already attached to it: alcohol)
Ethers
compounds where oxygen is bound to 2 carbon groups
Common name: cite the two groups attached + ether
IUPAC: ether is NOT treated as principal group; alk-oxy (substituent)
-if hanging out with ethane: ethoxy
-can be part of Cyclic structure: heterocyclic compound (has an atom other than C)
Sulfides (thioethers)
compounds where sulfur is bound to 2 carbon groups
Common name: cite the two groups attached + sulfide
IUPAC: sulfide is NOT treated as principal group; alkyl-thio (substituent)
-if hanging out with methane: methylthio
Alpha Carbon
carbon bonded to a halogen (alkyl halide) or oxygen (alcohol)
-aids in classification of alkyl halides and alcohols (primary: has one other group aside from OH/halide; secondary, so on…)
Wacky Groups
Allyl
H2C = CH - CH2 - R
Styrene
Ph - CH = CH2
Glycols
compounds that contain two or more hydroxy groups (-OH) on different carbons
Epoxides
Cyclic ethers
Bond Angles
alkyl halides, alcohols, thiols, ethers, sulfides: alpha carbons are sp3 so bond angles are almost tetrahedral
at O: sp2 so bond angles change (there’s an unbound electron pair) - greater than 90
at S: angles are close to 90
Noncovalent interactions
steric
intramolecular attraction - energetically favorable interactions
intramolecular repulsion - energetically unfavorable interactions
-reason behind solid and liquid states existing (noncovalent interactions because they don’t go through a chem reaction when they change phases)
Induced Dipole
complementary dipole that arises momentarily from the random movements of electrons in an electron cloud
when the positive end of a molecule is attracted to the negative end of another, there are van der Waals attractions or dispersion interaction
larger molecules have greater BP as van der Waals increase with surface area (branched molecules have low surface area and are too circular)
Polarizability
measure of how easily an external charge (dipole) can alter electron distribution of a molecule
(more polarizable = easily deformed electron clouds)
*electronegative atoms are not very polarizable
*more polarizable: higher boiling points
Permanent Dipoles
-molecules can have enhanced intermolecular attractions (interactions between molecules of the same species)
*high BP as compared to molecules of same shape and mass without them
Nitriles
-have unusually large dipole moments
- C (3x bond) N (two unpaired electrons)
Hydrogen Bond
weak covalent interaction + electrostatic attraction of opposite charges
-happens in water + alcohol
*very high BP
Melting Points
symmetrical compounds have higher (allows them to pack closer together) (and can have stronger noncovalent attractions)
(doesn’t matter to boiling points so it must only have relevance to solid states)
*free energy of fusion
*symmetrical compounds gain less entropy when they melt
Solutions
-if in separate phases, they’re insoluble; if they become a single liquid phase, they are soluble
-solvent shell (solvent molecules directly in contact with solute): may be multiple layers; dynamic - solvent molecules are constantly exchanging
*free energy of solution
change in G = G(solution) - [G(pure solute) + G(pure solvent)]
change in G < 0 (favorable - solution has lower energy than solute and solvent separately)
change in G > 0 (unfavorable)
Solvents
Protic - H-bond donor (water, alcohols, carboxylic acids
Aprotic - ether, dichloromethane, hexane
Polar (high dielectric constant – property of many molecules versus dipole moment is of individual molecules) or apolar
Donor (Lewis base) or nondonor
Polar vs Apolar
Polar - have significant dipole moments
Apolar - may or may not have dipolar molecules
