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functional groups
groups of atoms within a molecule that have characteristic chemical behaviors.
alkanes
cmpds compsed of carbon atoms connected via c-c single bonds also known as aliphatic cmpds
hydrocarbons
cmpds composed only of carbons and hydrogens
saturated alkanes and hydrocarbons
only contain c-c and C-H single bonds. Max # of H's per carbon atom CH3CH2CH3--> C3H8
Methane
CH4 1 C
Ethane
C2H6 2 carbons
propane
C3H8 3 carbons
Butane
C4H10 4 Cs
Pentane
C5H12 5 carbons
Hexane
C6H14 6 Cs
Heptane
C7H16 7 carbons
Octane
C8H18 8 carbons
nonane
C9H20 nine carbons
decane
C10H22
straight chain alkanes
cmpds that have carbons atoms connected in a single row
branched chain alkanes
exactly that they sound like-straight chains with branches
isomers
cmpds that have the same molecular formula but different structures.
constitutional isomers
cmpds that have the same numner and kind of atoms but differ in how the atoms are arranged (bonded)
characteristics of constitutional isomers
-different carbon skeletons -diff. functional groups -diff. funtional group location in the carbon chain
alkane groups
take away a H to make into alkyl groups CH4 (Methane)--> -H = CH3 (Methyl)
(Naming Alkanes) IUPAC
International Union of Pure and Applied Chemistry 3 parts to IUPAC name 1. prefix 2. parent 3. suffix
prefix (alkanes)
indicates where the substiuents are found
parent (alkanes)
how many carbons are in the parent chain
suffix (alkanes)
indicates what family/grouping the cmpd belongs to
chemical properties of Alkanes
-show little reactivity -react with oxygen and halogens (Cl, Br, I...)
physical properties of alkanes
-as molecular weight increases so does the melting point and boiling point -dispersion forces increase as molecular size increases -MP and BP increase as well
Phys Properties cont.
increased branching lowers an alkanes boiling pt because : -more spherical in nature than straight chains -smaller surface area of contact (dispersion forces minimized) -smaller dispersion forces overall
stereochemistry (alkanes)
systematic study of the 3D arrangement of atoms in a molecule
conformations (alkanes)
3D shape of a molecule at any given instant (assuming that rotation around single bond is frozen) *they are at equilibrium at room temp
conformers (alkanes)
conformational isomers -isomers that differ in the spatial orientation of thier atoms due to conformational changes (rotation of bonds)
sawhorse representations
-shows the molecule from an angle -shows all C-C/ C-H bonds
Newman projections
-shows the molecule looking down a specific C-C bond -shows all C-H bonds
conformations of butane
-anti (2 methyl groups are 180 degrees away from each other) -gauche ( 2 methyl groups are 60 degrees apart)
spectroscopy
uses infrared light to identify functional groups -interaction of electromagnetic energy with organic molecules
frequency
# of waves passed a fixed point per unit of time S-1 aka Hertz
amplitude
height of a wave wavelength * freq. = speed cm/s
E
amount of energy in one photon (quantum) of a given frequency
exposure of an organic molecule to electromagnetic radiation:
-absorption of E of certain wavelengths -transmitted E of certain wavelenghts
physical properties (cycloalkanes)
-melting pts do not follow a set trend due to differing ring shapes that effect crystal formationĀ  -Bps increase with molecular weight
cylcoalkanes physical properties
less flexible than open chain alkanes -alkanes have free rotation around the C-C single bond ( end to end sigma overlap) -cannot fully rotate around thier C-C single bonds w/o breaking open the ring
common ring sizes
C3-C7 (are extremely restricted in thier flexibilty -cannot fully rotate around their C-C bonds w/o breaking open the ring
consequence of cycloalkane
-has 2 sides -tope face -bottom face
cycloalkane isomerization
(cis-trans) differ from constitutional isomers -same order of atom connectivity -differ in spatial arrangement of thier atoms
stereoisomers
cmpds that have thier atoms connected in the same order but differ in thier spatial arrangementĀ  (3D) -cis ( same side) -trans (accross)
stablilty of cycloalkanes (Baeyer strain theory)
-because carbon prefers to have bond angles of 109.5 degrees ring sizes other than 5 or 6 atoms may be too "strained" to exist
nature of ring strain
-rings larger than 3 atoms are not flat -cyclic molecules can assume nonplanar conformations to minimize angle strain and torsional strain. "ring puckering" -large rings have more attainable conformations then smaller ones
angle strain
expansion or compression of bond angles away from a stable 109.5 degress
torsional strain
eclipsing of bonds on neighboring atoms (e- repulsion)
steric strain
repulsive interactions b/w nonbonded atoms in close proximity
cyclopropane
-a three membered planar ring structure -symmetrical ring w/ C-C-C bond angles of 60 degrees -requires "bent" sp3 based C-C sigma bonds (weaker=more reactive) -all of C-H bonds are fully eclipsed (torsional strain)
bent bonds of cyclopropane
-electron density of the C-C bond is displaced outward from the inter nuclear axis
cyclobutane
-has less angle strain than cyclopropane -has more torsional strain -slightly bent out of plane 1 carbon is 25 degrees above/below plane -increasing angle strain but decreasing torsional strain
cyclopentane
-planar structure would have no angle strain but high amounts of torsional strain -cyclopentane is nonplanar in order to reduce torsional strain -four carbons are in plane while the fiffth atom is slightly ablove/below plane.
conformations of cyclohexane
-occur commonly/widely in nature -free of angle strain and torsional strain -most stable 3-D conformation has altering atoms in a common plane. optimal tetrahedral bond angles as achieved around each carbon atom
axial and equatorial bonds pt 1
a chair conformation has 2 types of substiuent positions: -axial-->6 Hs perpindicular to ring -equatorial-->6 Hs near the plane of the ring ( equator)
axial and equatorial bonds pt 2
-each carbon atom in cyclohexane has one axial and one equatorial hydrogen bond -each face of a cyclohexane ring has 3 axial and 3 equatorial Hs (bonds)

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