Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
MODEL FOR DEMONSTRATION OF C}iEMICAL BONDIhlG
This invention rela-tes to a model assembly for the
purpose of the teaching of chemical bonding, particularly of
multiple bonding.
The teaching of chemical bonding requixes of the
teacher ways oE clarifying and illustrating in positive manner
implied theoretical concepts and the teacher has to rely on
personal artistic ability to repxesent on a two-dimensional
black-board a reality which,in fact, is three dimensional. Black-
board presentations and all known teaching attempts have the
drawback that they are static representa-tions of a phenomenon
which is dynamic.
The present invention overcomes these di~ficulties by
providing a dynamic representation of a phenomenon which has
previously been generally demonstrated in a two-dimensional,
or static way, for example, by way of black-board or pictorial
; xepresentations. All presently existing models of carbon-carbon
double bonds (oleEinic bonds), represent -the type of bonding
after the molecule has formed and with these presen-t models one
can see the molecular geometry; -the planarity of the molecule;
the bond angles and to some extent, the overlap of bonding orb-
itals. The present invention elimina-tes the tendency of students
of the previous art to perceive a triple bond rather than a double
bond especially in the static graphic representations, such as
black-boards or printed illustrations, after the molecule is
formed~ The present invention also allows students to visualize
the dynamics o-f olefinic bond forma-tion; to consider the plan-
arity of the molecule; -the various axes of the bonds; the ex-
30 terior axis of the ~ (pi) bond and the re-distribution of the -~
bond angles in the plane and this can be seen, not after the
double bond has been foxmed, but simultaneously as the overlap
-1-
7~3
of "p" orbi-tals and of ~Sp2~ upon "Sp2" occurs.
Tlle black-board illustrations and the previously known
art have a drawback in that they are static representations of
a phenomenon which is dynamic. AS discussed above, existing
models of the carbon-carbon double bonds, (ole~inic bonds), re-
present the type of bonding after the molecule has formed and
the students see the molecular geometry; the planari-ty of the
molecule; the bond angles and to some exten-t the overlap of bond-
ing orbitals. ~lowever, the less percep-tive students -tend to see
in the two-dimensional graphic illustrations and in some of the
models now marketedla triple bond rather than a double bond and
again they see this after -the molecule is formed, that is, in a
very static way.
The present inven-tion is an improvement over the pre-
viously known art, in that the present model assembly allows
students to visualize the dynamics of olefinic bond formation.
It allows the students to consider the planarity oE the molecule;
the various axes of the siyma bonds; the external la-teral ~ bond
and the re-distribution of the bond angles in the plane. This
can be seen, not after the double bond has foxmed, but ~imu:Ltan-
eously as the overlap of "p" orbitals and of "sp2" upon "sp2"
orbi-tals, occurs.
More specifically the present invention relates to a
teaching model assembly to dynamically demons-trate chemical bond-
ing particularly chemical double bonding, comprising
two spaced spheres representing carbon atoms, each
sphere carrying a fixed blade extending toward the other sphere
with the fixed blades representing a hybridized "sp " orbi-tal,
and each sphere carrying a blade represen-ting an
unhyhridized "p" orbital movable in a first plane toward the
other sphere to at least partially overlap or contact the cor~
responding blade carried by the o-ther sphere which has been moved
7~
toward the first sphere in -the first plane,
and each sphere carrying a pair of blades which each
represent hybridized "sp2" orbitals and which are simultaneously
- movable in a second plane which is normal -to -the first plane,
in each sphere the inner ends of the blade represent-
ing the unhybridized "p" orbital being interconnected wi-th the
inner ends of the blades movable in the second plane representing
hybridized "sp " orbitals whereby movement of the unhybridized
"p" orbital blade -toward the other sphere results in simultan-
eous movement of the related pair of hybridized "sp " orbitals
away from the other sphere to a position in the second plane where
the thre~ hybridized "sp " blades are separated by 120 .
BRIE~ DESCRIPTION OF ACCOMPANYING DR~WINGS
.... _ .. .
The inventive concept will now be more Eully described
with reEerence to the accompanying drawings wherein:
Figure 1 illustra-tes in front perspec-tive view a model
in accordance with the present invention;
Figure 2 is a top view oE a portion of the model as-
sembly as shown in Fiyure l;
Figure 3 is a side view of a portion, partially dis-
assembled, of -the model as shown in Figure l;
~igure 4 is a lock and pivotiny connection which may .
suitably be used with the present model; and
Figure 5 is an exploded presenta-tion oE upper and lower
halves of a sphere illustrating in perspective view the operative
components housed therein~
Reference will now be specifically had to the accom~
panying drawings wherein like reference numerals re~er to like
parts.
3~ D~SCRIPTION OF CONSTRUCTION
. . .
In the drawings, the large spheres ~ which may be
made of any suitable material represent carbon atoms.
7~3
The two spheres 2 are respectively suppor-ted by sup-
port rods 4 by a suitable lock and pivot arrangement shown gen-
erally by numeral 6. This arrangemen-t is detailed in Fiyure 4
which shows the inwardly poin-ting ends of support rods 4 provided
with undercut portions 8. A rod end is received wi-thin a bore
provided in support bracke-t 10 and upon -tightening of screw 12
the inner end of the screw enters undercut 8 to hold the support
bracket 10 on the rod end. The support bracke-t 10 is secured to
the spheres 2 by suitable means such as screws 14 as shown in
Figure 3. Such an arrangement permits -the spheres 2 to be
selectively rotated about and securely locked to the ends of
rods 4.
The lower ends of rods ~ are securel.y carried by a
base 16 which ~or convenience oE transportation and storage may
be provided as separate halves held together by a suitable sep-
arable magnet arrangement 18 shown in broken lines in Figure 1.
Each o.f the spheres 2 carry a movable blade 20 which
represent unhybridized "p" orbi-tals; and each sphere carries
two movable blades 21 which represent hybridized l'sp " orbital5
and a fixed blade 22 which represen-ts a hybridiæed "sp2ll orbital.
In the orientation o.E the model as shown in F'igures 1,
2 and 3, the blades 20 and 22 (and supplemental blade 20') are
in a vertical plane which is referred to as being a first plane
while the blades 21 are in a horizontal or second plane which is
normal to the first plane.
The blades 22 are securely fixed to each of their res-
pPctive spheres 2 whereas the blades 20 are free for movement from
a vertical position shown in broken lines in Figure 1 to a par-
tially overlapping position shown in -Eull lines in Figures 1 and
. 30 2.
The spheres 2 contain mechanism wherein movement of
blades 20 from the position shown in bro]cen lines in Figure 1
L3
to the posi-tion shown in full lines result in a correspondiny
horiz~n-tal movement of hlades 21 f~om -the posi-tion shown in
broken lines in E'igure 2 to the posi-tion shown in full lines in
Figures 1 and 2.
Various mechanisms may be employed to effect this re-
lated movement between blades 20 and 21 but one suitable arrange-
ment is shown in Figure 5 which will now be described in detail.
Each of the spheres 2 consist of upper and lower halves
26 and 28 and the inner ends of blades 21 are received within the
lower half and are pivotally mounted therein by bolts 30. Out-
wardly of these bolts 30 slot-ted bolt members 32 are pivotally
carried by the blades and are held thereon by nu-ts 34.
The lowermost end o~ blade 20 projects downwardly
throu~h a slot 36 providecl in the upper half 26 and is rotat-
ably mounted about a pivot pin 38 the encls o~ which are mounted
in brackets 40 which are in turn held within the upper sphere
by screws 42 in the manner as shown. The lowermost end of
blade 20 carries a rod 44, the outer ends of which are xeceived
(when the two halves are assembled) within the slots of slotted
members 32. By moving blade 20 about its pivot. pin 38 a corres-
ponding movement will then be imparted to blacles 21.
The outer ends of blades 21 may carry smaller spheres
46 shown in broken lines in Figures 1 and 2, and which represent
hydrogen atoms. The smaller spheres 46 may be fixedly secured
to the outer ends of the blades or alternatively the "hydrogen"
spheres 46 may be removably carried by the blades 21.
The blades 20, 21 and 22 may be made of any suitable
material and they may preferably be made of a transparent mater-
ial such as polymethymethacrylate. In preferred cons-truction the
blades 21 and 22 are smaller than blades 20 and 20'.
DESCRIPTION OF OPERATION AND USE
_
The mode of use and operation of the model assembly
is as Eollows:
Havin~ given the class all the necessary theory, ~he
teacher begins the demonstra-tion by pointing out what each part
represents, namely the carbon atoms, the hydrogen atoms, the
unhybricli~ed "p" orbitals and the "sp2" hybridized orbitals,
etc.
With blades 20 in the vertical position as shown in
broken lines in Figure 1, the two halves of the model assembly
are pushed towards one another so that the blades 22 are made to
overlap when the bases 16 touch one another. The overlap of
blades 22 simulates the formation of a ~ (sigma) bond between the
carbon atoms. The previously ver-tical blacles 20 are then pushed
inwardly slowly together as to effect the overlap of blades 20
over 20 as shown in full ~nes in Figures ~ and 2. I'his simulates
the lateral overlap of unhybridi7.ed "p" over "p" orbitals which
form the ~f(pi) bond.
When both blades 20 are fully pushed towards one an-
other, as shown in full lines in Figures 1 and 2 the blades 21
will be forced in the opposite direction i.e., -towards the ends
of the model assembly as shown in full lines in Figures 1 and 2.
The linkage mechanism buil-t into -the spheres 2 is dis-
posed and adapted so that when overlap o-E the unhybridi~ed "p"
orbital blades 20 is effected, the blades 21 all move in the
same plane and assu~e within -tha-t plane a symme-trica:L distribut-
ion about the carbon atoms. When viewed from above, as shown in
Figure 2, the angles bet~een the central carbon-carbon bonds 20,
22 and ~he external carbon-hydrogen bonds (bonds be-tween spheres
2 and spheres ~6) are of 120.
At this point, students can see -the overlap of the
sp - sp orbi-tals, the~ bond and also the overlap of the p-p
orbitals, the ~ bond, external to the main c-c axis. From -their
vantage point, students like~ise see the geometric~l plane of -the
7~
represented molecule. However, they do not yet see -the angular
distribution of the bonds. In order to give a top view, the
teacher loosens the locking screws 12 and rotates the entire mol-
ecular model suspended on rods ~ to a position faciny the students
which is equivalent to viewing from above.
Overlap above or below a horizontal plane can ~e
simulated or represen-ted by the rotation o-f the entire model
structure about its horizontal axis, by loosening the end lock-
ing screws 12.
In order to avoid the appearance of a triple bond, the
model assembly shown has only one-half of the unhybridized "p"
orbital blades 20.
As shown in Figure l and to represent the simultaneous
above and below overlap, a second half of a "p" orbital blade
20' can be attached magnetically, to the lower inner side of
the spheres once they are in -the proper positions. The posi-tion-
ing of blade 20' is shown in broken lines in Figure l.
These features, along with -the size of -the model,
which can be built to scale, grea-tly facilitate stuclen-t compre-
hension and the model i-tself is ideal to illustrate chemical
bonding to large classes of students by visual means.
In the foregoing description and accompanying claims,
reference is made to vertical (first) and horizontal (second)
planes and this terminology is used for understanding and defini-
tion only ~ithout limitation as -to how the model assembly may
be oriented when in use.
