Chapter 4: Alkanes Flashcards
[4.1] What is the molecular formula of acyclic alkanes?
CnH2n+2
[4.1] What is the molecular formula of cyclic alkanes?
CnH2n
[4.1] This type of isomer differs in the way the atoms are connected to each other
constitutional isomers
[4.1] What do you call a CH2 group
methylene
[4.1] a group of compounds that differ by only a CH2 group is called a?
homologous series
[4.2] Prefix used for naming cycloalkanes
cyclo-
[4.3] What does IUPAC stand for?
International Union of Pure and Applied Chemistry
[4.4] What do you create removing one hydrogen from an alkane
Alkyl group
[4.8] Are alkanes water or fat soluble?
Fat soluble
[4.8] In alkanes, what is the relationship of MP and BP in the number of carbons?
Direct
[4.8] In alkanes, what is the relationship of BP and branching?
Indirect
[4.8] In alkanes, what is the relationship of MP and symmetry?
Direct
[4.9] What do you call the different arrangements of atoms that are interconverted by rotation around single bonds? What are its two types?
Conformations, eclipsed and staggered
[4.9] rotating the atom on one carbon by how many degrees converts an eclipsed conformation into a staggered conformation, and vice versa?
60°
[4.9] What is the angle that separates a bond on one atom from a bond on an adjacent atom
dihedral angle
[4.9] What are the end-on representations for conformations, the circle representing the back carbon and the dot representing the front carbon
Newman projections
[4.9] Which of the two conformations are less stable, and why?
Eclipsed, because of electron-electron repulsion
[4.9] The difference in energy between the staggered and eclipsed conformations is _ kJ/mol (_ kcal/mol)?
12; 2.9
[4.9] What is the energy difference between staggered and eclipsed conformations
Torsional energy
[4.9] What is an increase in energy caused by eclipsing interactions; strain causes an energy increase
Torsional strain
[4.9] What conformations are energy minimum and energy maximum?
Energy minimum - staggered conformation, most stable
Energy maximum - eclipsed conformation, least stable
[4.10] It takes how many 60° rotations to return to the original conformation?
six
[4.10] a staggered conformation with two larger groups 180° from each other
anti
[4.10] a staggered conformation with two larger groups 60° from each other
gauche
[4.10] an increase in energy resulting when atoms are forced too close to one another
steric strain
[4.10] which is higher in energy, gauche or anti?
gauche
[4.10] what is the energy difference between the lowest and highest energy conformations
barrier to rotation
[4.11] What is the strain caused by an increase in energy when tetrahedral bond angles deviate from the optimum angle of 109.5°
angle strain
[4.11] What is the assumption that rings with bond angles so different from the tetrahedral bond angle would be very strained an highly reactive
Baeyer strain theory
[4.12] What is the most common ring size in naturally occurring compounds
cyclohexane
[4.12] How does cyclohexane eliminate angle strain?
all C-C-C bond angles are 109.5°
[4.12] How does cyclohexane eliminate torsional strain?
all hydrogens on adjacent carbon atoms are staggered, not eclipsed
[4.12] The process by which ring bonds twist and bend in a more restricted way; conformational change
ring-flipping
[4.12] What is the intermediate conformation during ring flipping?
Boat conformation
[4.12] What do you call the hydrogens forced close to each other during boat conformation
Flagpole hydrogens
[4.13] In a disubstituted cyclohexane, each of the two stereoisomers (cis and trans) has how many possible chair conformations?
two
